                               
















                           LXT-200S

                    Product Specification
                   and OEM Technical Manual























       Document 1018328
       Revision B
       January 1990

Address comments concerning this manual to:
Maxtor Corporation
Technical Publications
211 River Oaks Parkway
San Jose, California 95134-1913
Telephone:  (408) 432-1700
Telex:  171074
FAX:  (408) 434-6469










Technical Data Restrictions

In case of sale to or use of units by DoD: Use, duplication or
disclosure of  any software, firmware or related documentation
is subject to restrictions stated in paragraph (c) (1) (ii) of
the Rights  in Technical  Data and Computer Software clause at
DFAR 252.227-7013.   For Civilian Agencies: Use, reproduction,
or disclosure  of the  software and  related documentation  is
subject  to   restrictions  set   forth  in   FAR   52.227-19.
Unpublished rights  reserved under  the copyright  laws of the
United States.   Maxtor  Corporation, 211  River Oaks Parkway,
San Jose, CA 95134.










Copyright Notice

This manual  and all material contained in it are copyrighted.
The manual may not be copied, in whole or in part, without the
written consent  of Maxtor  Corporation.  The contents of this
manual may be revised without prior notice.

  Copyright 1989 by Maxtor Corporation, San Jose, California,
USA.  All rights reserved









PREFACE
       The purpose  of this  manual is  to provide  all of the
       technical information  you need  to install and use the
       Maxtor LXT-200S Family disk drives.  It is intended for
       evaluation and  integration engineers  who are building
       or assembling  a total  computer system.   This  manual
       does not include the information needed to repair these
       disk drives.   For  this information contact the Maxtor
       Service Center in San Jose, CA.

       Chapter 1  is a complete description of the disk drive,
       including  specifications.    Chapter  2  provides  the
       information you  need to  prepare the  disk  drive  for
       installation.   Chapter 3 covers installation.  Chapter
       4 provides  information on  the daily  function of  the
       disk drive.   Chapter 5 begins the interface discussion
       by  including   information  on  the  various  possible
       configurations  and   on  the   electrical   interface.
       Chapter 6  continues the  discussion on  the  interface
       with  information  on  the  SCSI  phases.    Chapter  7
       concludes the  interface discussion with information on
       the SCSI commands that the disk drive supports.

       Maxtor publishes descriptive brochures and data sheets,
       this original  equipment manufacturer  (OEM)  technical
       manual, and  a quick  reference guide  for each product
       line.   Changes that  affect the  content of any manual
       are covered  by addenda  or revisions  to the  affected
       manual.

       Maxtor  reserves  the  right  to  make  changes  and/or
       improvements to  its  products  without  incurring  any
       obligation to  incorporate such changes or improvements
       in units previously sold or shipped.


REFERENCE NUMBERS

       For information  concerning drive set-up and operation,
       contact Maxtor Technical Support at (408) 432-4893.

       For  information   regarding  PC   AT/XT,  PS-2,  and
       Macintosh  applications,  contact  Storage  Dimensions
       Inc.  (SDI)   Technical  Support   at  (408)  395-2688,
       extensions 278-281.
                               

                       REVISION RECORD


                               

           Revision Date Published    Revised Contents



            01      December 1988     Preliminary Release


            02      January 1989      Preliminary Release


            A       April 1989        Formal Release


            B       January 1990      Formal Release



                    Document No:  1018328

                           WARRANTY

Maxtor warrants  the LXT-200S  Family of  disk drives  against
defects in  materials and  workmanship for  a period of twelve
months for  the original  purchaser.    Direct  any  questions
regarding the  warranty to  your Maxtor  Sales Representative.
Maxtor  maintains   Customer  Service   Centers  for  the  re-
pair/reconditioning  of  all  Maxtor  products.    Direct  all
requests for  repair to the Maxtor Service Center in San Jose.
This assures you of the fastest possible service.

                     REGULATORY APPROVALS

         UL Recognition obtained:  Application submitted
         CSA Certification obtained:    Application submitted
         VDE Recognition:          Application submitted
















 LXT-200S Family Product Specification & OEM Technical Manual


                      TABLE OF CONTENTS

 LXT-200S Family Product Specification & OEM Technical Manual


                      TABLE OF CONTENTS


PREFACE...................................................III


REFERENCE NUMBERS.........................................III


1.0....................................DISK DRIVE DESCRIPTION   
   1

  1.1..................................Product Specifications   
      5
     1.1.1.........................Performance Specifications   
          6
     1.1.2..........................Functional Specifications   
          8
     1.1.3.......................Environmental Specifications   
          9
     1.1.4............................Physical Specifications   
          10
     1.1.5.........................Reliability Specifications   
          10
     1.1.6........................................Error Rates   
          11
     1.1.7..............................DC Power Requirements   
          12
     1.1.8..........................Standards and Regulations   
          12
  1.2.............................................Major Parts   
      13
     1.2.1..............................Air Filtration System   
          13
     1.2.2....................................Drive Mechanism   
          14
     1.2.3.........................Head Positioning Mechanism   
          15
     1.2.4.........................Read/Write Heads and Disks   
          16

2.0..........................................DISK DRIVE SETUP   
   17

  2.1.......................................SCSI ID Selection   
      17
  2.2..................................Drive Power-Up Options   
      18




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                      TABLE OF CONTENTS

  2.3..............................Terminator Power Selection   
      19
  2.4...................................Parity Disable Option   
      19
  2.5.............................................Sector Size   
      19
  2.6...................................Interface Termination   
      19
  2.7.......................................Service Connector   
      20
  2.8.........................Spindle Synchronization Control   
      22

3.0...................................DISK DRIVE INSTALLATION   
   23

  3.1................................................Mounting   
      23
  3.2........................................Power-Up Testing   
      26
     3.2.1.................................Self-Test Sequence   
          27
     3.2.2............................Initialization Sequence   
          28
     3.2.3.................................Self-Configuration   
          28
     3.2.4...........................UNIT ATTENTION Condition   
          28
     3.2.5...................................Buffering Scheme   
          29
  3.3................................................Shipping   
      29

4.0................................DISK DRIVE DAILY OPERATION   
   31

  4.1......Read/Write Control and SCSI Controller Electronics   
      31
  4.2.................................Track and Sector Format   
      32

5.0.................................................INTERFACE   
   33

  5.1..........................................SCSI Interface   
      33
     5.1.1....................Initiator-Target Configurations   
          33
     5.1.2..............Logical/Electrical Signal Definitions   
          35





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                      TABLE OF CONTENTS

     5.1.3......................Pin Assignments and Connector   
          36
  5.2..............................Electrical Power Interface   
      39
     5.2.1..................................Power-Up Sequence   
          39
     5.2.2....................................Power Connector   
          40

6.0...............................................SCSI PHASES   
   41

  6.1..........................................BUS FREE Phase   
      42
  6.2.......................................ARBITRATION Phase   
      43
  6.3.........................................SELECTION Phase   
      43
  6.4.......................................RESELECTION Phase   
      43
  6.5.............................Information Transfer Phases   
      44
     6.5.1..................Asynchronous Information Transfer   
          45
     6.5.2..........................Synchronous Data Transfer   
          46
     6.5.3......................................COMMAND Phase   
          47
     6.5.4........................DATA IN and DATA OUT Phases   
          47
     6.5.5.......................................STATUS Phase   
          47
     6.5.6......................................MESSAGE Phase   
          49
       A.....................................MESSAGE IN Phase   
          50
       B....................................MESSAGE OUT Phase   
          50
       C...............................COMMAND COMPLETE (00h)   
          51
       D..............................SAVE DATA POINTER (02h)   
          51
       E...............................RESTORE POINTERS (03h)   
          51
       F.....................................DISCONNECT (04h)   
          52
       G.......................INITIATOR DETECTED ERROR (05h)   
          52
       H..........................................ABORT (06h)   
          52





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                      TABLE OF CONTENTS

       I.................................MESSAGE REJECT (07h)   
          52
       J...................................NO OPERATION (08h)   
          53
       K...........................MESSAGE PARITY ERROR (09h)   
          53
       L........................LINKED COMMAND COMPLETE (0Ah)   
          53
       M............LINKED COMMAND COMPLETE (WITH FLAG) (0Bh)   
          53
       N...............................BUS DEVICE RESET (0Ch)   
          54
       O...................................IDENTIFY (C0h/80h)   
          54
  6.6.........SYNCHRONOUS DATA TRANSFER REQUEST Message (01h)   
      54
  6.7........................................Error Conditions   
      56
     6.7.1.....................MESSAGE OUT Phase Parity Error   
          56
     6.7.2.........................COMMAND Phase Parity Error   
          57
     6.7.3........................DATA OUT Phase Parity Error   
          57
     6.7.4...........................Initiator Detected Error   
          57
     6.7.5...................................REJECTED Message   
          58
     6.7.6.....................Initiator MESSAGE PARITY ERROR   
          58
     6.7.7...............................RESELECTION Time-Out   
          59
     6.7.8.........................Internal Controller Errors   
          59

7.0.................................SCSI COMMAND DESCRIPTIONS   
   61

  7.1...................................SCSI Command Overview   
      61
  7.2.......................................FORMAT UNIT - 04h   
      66
     7.2.1.............................Defect List Management   
          66
     7.2.2....................................SCSI Deviations   
          67
     7.2.3.................................Command Parameters   
          68
     7.2.4.......................................Format Modes   
          69





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                      TABLE OF CONTENTS

     7.2.5..............................Initiator Defect List   
          71
       A.......................D List Bytes from Index Format   
          72
       B........................D List Physical Sector Format   
          73
     7.2.6...................................Error Conditions   
          74
  7.3...........................................INQUIRY - 12h   
      76
     7.3.1....................................SCSI Deviations   
          76
     7.3.2.................................Command Parameters   
          76
     7.3.3........................................Data Format   
          77
  7.4.......................................MODE SELECT - 15h   
      79
     7.4.1....................................SCSI Deviations   
          80
     7.4.2.................................Command Parameters   
          80
     7.4.3..............................Parameter List Format   
          81
       A.........................Parameter List Header Format   
          81
       B...............Parameter List Block Descriptor Format   
          82
       C...................................Page Header Format   
          83
     7.4.4.....................Error Recovery Parameters Page   
          84
     7.4.5...............Disconnect/Reconnect Parameters Page   
          89
     7.4.6........Direct-Access Device Format Parameters Page   
          90
     7.4.7..........Rigid Disk Drive Geometry Parameters Page   
          93
     7.4.8............................Read-Ahead Control Page   
          94
     7.4.9...................................Error Conditions   
          96
  7.5........................................MODE SENSE - 1Ah   
      98
     7.5.1....................................SCSI Deviations   
          99
     7.5.2.................................Command Parameters   
          99
     7.5.3..............................Parameter List Format   
          101





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                      TABLE OF CONTENTS

       A.........................Parameter List Header Format   
          102
       B...............Parameter List Block Descriptor Format   
          103
       C...................................Page Header Format   
          104
     7.5.4.....................Error Recovery Parameters Page   
          104
     7.5.5...............Disconnect/Reconnect Parameters Page   
          107
     7.5.6........Direct-Access Device Format Parameters Page   
          109
     7.5.7..........Rigid Disk Drive Geometry Parameters Page   
          112
     7.5.8.................Read-Ahead Control Parameters Page   
          113
     7.5.9...................................Error Conditions   
          115
  7.6..............................................READ - 08h   
      116
     7.6.1....................................SCSI Deviations   
          116
     7.6.2.................................Command Parameters   
          116
     7.6.3...................................Error Conditions   
          117
  7.7...................................READ (EXTENDED) - 28h   
      118
     7.7.1....................................SCSI Deviations   
          118
     7.7.2.................................Command Parameters   
          118
     7.7.3...................................Error Conditions   
          119
  7.8.......................................READ BUFFER - 3Ch   
      120
     7.8.1....................................SCSI Deviations   
          120
     7.8.2.................................Command Parameters   
          120
     7.8.3......................................Command Usage   
          121
     7.8.4........................................Data Format   
          121
     7.8.5...................................Error Conditions   
          122
  7.9.....................................READ CAPACITY - 25h   
      123
     7.9.1....................................SCSI Deviations   
          123





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                      TABLE OF CONTENTS

     7.9.2.................................Command Parameters   
          123
     7.9.3........................................Data Format   
          124
     7.9.4...................................Error Conditions   
          125
  7.10.................................READ DEFECT LIST - 37h   
      126
     7.10.1...................................SCSI Deviations   
          126
     7.10.2................................Command Parameters   
          126
     7.10.3............................................Header   
          128
     7.10.4...........................Bytes from Index Format   
          129
     7.10.5............................Physical Sector Format   
          130
     7.10.6..................................Error Conditions   
          131
  7.11....................................READ LONG - E8h/3Eh   
      132
     7.11.1...................................SCSI Deviations   
          132
     7.11.2................................Command Parameters   
          132
     7.11.3..................................Error Conditions   
          133
  7.12...................................REASSIGN BLOCK - 07h   
      134
     7.12.1...................................SCSI Deviations   
          134
     7.12.2................................Command Parameters   
          134
     7.12.3................................Defect List Format   
          135
     7.12.4..................................Error Conditions   
          136
  7.13.......................RECEIVE DIAGNOSTIC RESULTS - 1Ch   
      137
     7.13.1...................................SCSI Deviations   
          137
     7.13.2................................Command Parameters   
          137
     7.13.3.......................................Data Format   
          138
     7.13.4..................................Error Conditions   
          138
  7.14.....................................RELEASE UNIT - 17h   
      139





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                      TABLE OF CONTENTS

     7.14.1...................................SCSI Deviations   
          139
     7.14.2................................Command Parameters   
          139
     7.14.3..................................Error Conditions   
          140
  7.15....................................REQUEST SENSE - 03h   
      141
     7.15.1...................................SCSI Deviations   
          141
     7.15.2................................Command Parameters   
          141
     7.15.3.......................................Data Format   
          142
       A...........................Extended Sense Data Format   
          143
       B..........................................Sense Codes   
          147
     7.15.4..................................Error Conditions   
          150
  7.16.....................................RESERVE UNIT - 16h   
      151
     7.16.1...................................SCSI Deviations   
          151
     7.16.2................................Command Parameters   
          151
     7.16.3..................................Error Conditions   
          152
  7.17......................................REZERO UNIT - 01h   
      153
     7.17.1...................................SCSI Deviations   
          153
     7.17.2................................Command Parameters   
          153
  7.18.............................................SEEK - 0Bh   
      154
     7.18.1...................................SCSI Deviations   
          154
     7.18.2................................Command Parameters   
          154
     7.18.3..................................Error Conditions   
          155
  7.19..................................SEEK (EXTENDED) - 2Bh   
      156
     7.19.1...................................SCSI Deviations   
          156
     7.19.2................................Command Parameters   
          156
     7.19.3..................................Error Conditions   
          157





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                      TABLE OF CONTENTS

  7.20..................................SEND DIAGNOSTIC - 1Dh   
      158
     7.20.1...................................SCSI Deviations   
          158
     7.20.2................................Command Parameters   
          158
     7.20.3..................................Error Conditions   
          159
  7.21..................................START/STOP UNIT - 1Bh   
      160
     7.21.1...................................SCSI Deviations   
          160
     7.21.2................................Command Parameters   
          160
     7.21.3..................................Error Conditions   
          161
  7.22..................................TEST UNIT READY - 00h   
      162
     7.22.1...................................SCSI Deviations   
          162
     7.22.2................................Command Parameters   
          162
     7.22.3..................................Error Conditions   
          162
  7.23...........................................VERIFY - 2Fh   
      163
     7.23.1...................................SCSI Deviations   
          163
     7.23.2................................Command Parameters   
          163
     7.23.3..................................Error Conditions   
          164
  7.24............................................WRITE - 0Ah   
      165
     7.24.1...................................SCSI Deviations   
          165
     7.24.2................................Command Parameters   
          165
     7.24.3..................................Error Conditions   
          166
  7.25.................................WRITE (EXTENDED) - 2Ah   
      167
     7.25.1...................................SCSI Deviations   
          167
     7.25.2................................Command Parameters   
          167
     7.25.3..................................Error Conditions   
          168
  7.26.................................WRITE AND VERIFY - 2Eh   
      169





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                      TABLE OF CONTENTS

     7.26.1...................................SCSI Deviations   
          169
     7.26.2................................Command Parameters   
          169
  7.27.....................................WRITE BUFFER - 3Bh   
      171
     7.27.1...................................SCSI Deviations   
          171
     7.27.2................................Command Parameters   
          171
     7.27.3.......................................Data Format   
          172
     7.27.4..................................Error Conditions   
          173
  7.28...................................WRITE LONG - EAh/3Fh   
      174
     7.28.1...................................SCSI Deviations   
          174
     7.28.2................................Command Parameters   
          174
     7.28.3..................................Error Conditions   
          175

APPENDIX A:  CDB BIT DEFINITIONS..........................177


APPENDIX B:  UNITS OF MEASURE.............................178


LIST OF ABBREVIATIONS.....................................179


GLOSSARY..................................................183






















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 LXT-200S Family Product Specification & OEM Technical Manual


                           FIGURES

 LXT-200S Family Product Specification & OEM Technical Manual


                           FIGURES

Figure 11................................LXT-200S Disk Drive   
1
Figure 12..............................Air Filtration System   
14
Figure 13.........................Head Positioning Mechanism   
15
Figure 21.........................................PCB Layout   
17
Figure 22...........Connector Locations, Front View of Drive   
21
Figure 31.............Mechanical Outline, Top and Side Views   
24
Figure 32.................Mechanical Outline, Isometric View   
25
Figure 33................................Removable Faceplate   
26
Figure 41.......................................Track Format   
32
Figure 51........................Typical SCSI Configurations   
34
Figure 52............Connector Locations, Rear View of Drive   
38
Figure 53...............................SCSI Cable Connector   
39
Figure 54.......................................J3 Connector   
40
Figure 61..............Signal Sequence Chart for SCSI Phases   
42






















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 LXT-200S Family Product Specification & OEM Technical Manual


                            TABLES

 LXT-200S Family Product Specification & OEM Technical Manual


                            TABLES

Table 11..........................Performance Specifications   
6
Table 12...........................Functional Specifications   
8
Table 13................................Environmental Limits   
9
Table 14.................................Physical Dimensions   
10
Table 15..........................Reliability Specifications   
10
Table 16.........................................Error Rates   
11
Table 17...............................DC Power Requirements   
12
Table 21.....................................SCSI ID Jumpers   
18
Table 22.........................Summary of Power-Up Options   
18
Table 23...................Service Connector Pin Assignments   
21
Table 51...........................Connector Pin Assignments   
37
Table 61........................Signal States and Bus Phases   
41
Table 62.....................................SCSI Bus Timing   
45
Table 63.........................................Status Byte   
48
Table 64........................................Status Codes   
48
Table 65.......................................Message Codes   
50
Table 66..............................IDENTIFY Message Codes   
54
Table 67.......SYNCHRONOUS DATA TRANSFER REQUEST Byte Values   
55
Table 71.....................Typical CDB for 6-Byte Commands   
61
Table 72....................Typical CDB for 10-Byte Commands   
62
Table 73...........................CDB Operation Code Format   
63
Table 74.................................CDB Operation Codes   
63
Table 75........................................Control Byte   
64




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                            TABLES

Table 76.....................................FORMAT UNIT CDB   
68
Table 77......................FORMAT UNIT Defect List Header   
70
Table 78......................FORMAT UNIT Drive Format Modes   
71
Table 79..........................FORMAT UNIT D List Formats   
72
Table 710.FORMAT UNIT Defect Descriptor(s), Bytes from Index
Format  73
Table 711..FORMAT UNIT Defect Descriptor(s), Physical Sector
Format  74
Table 712........................................INQUIRY CDB   
76
Table 713..............................INQUIRY Response Data   
77
Table 714....................................MODE SELECT CDB   
80
Table 715..................MODE SELECT Parameter List Header   
82
Table 716.MODE SELECT Parameter List Block Descriptor Format   
83
Table 717.............................MODE SELECT Page Codes   
84
Table 718MODE SELECT Error Recovery Parameters (Page Code 1)   
85
Table 719...................MODE SELECT Error Recovery Modes   
88
Table 720MODE SELECT Disconnect/Reconnect Control Parameters
(Page Code 2)..............................................89
Table 721.MODE SELECT Direct-Access Device Format Parameters
(Page Code 3)..............................................91
Table 722...MODE SELECT Rigid Disk Drive Geometry Parameters
(Page Code 4)..............................................93
Table 723..MODE SELECT Read-Ahead Control Page (Page Code 8)   
95
Table 724.....................................MODE SENSE CDB   
99
Table 725.....................MODE SENSE Page Control Fields   
100
Table 726..............................MODE SENSE Page Codes   
101
Table 727...................MODE SENSE Parameter List Header   
102
Table 728..MODE SENSE Parameter List Block Descriptor Format   
103
Table 729..............................MODE SENSE Page Codes   
104
Table 730.MODE SENSE Error Recovery Parameters (Page Code 1)   
105

 LXT-200S Family Product Specification & OEM Technical Manual


                            TABLES

Table 731.MODE SENSE Disconnect/Reconnect Control Parameters
(Page Code 2).............................................108
Table 732..MODE SENSE Direct-Access Device Format Parameters
(Page Code 3).............................................110
Table 733....MODE SENSE Rigid Disk Drive Geometry Parameters
(Page Code 4).............................................112
Table 734MODE SENSE Read-Ahead Control Parameters (Page Code
8)      114
Table 735...........................................READ CDB   
116
Table 736................................READ (EXTENDED) CDB   
118
Table 737....................................READ BUFFER CDB   
120
Table 738.................................READ BUFFER Header   
122
Table 739..................................READ CAPACITY CDB   
124
Table 740..........................READ CAPACITY Data Format   
125
Table 741...............................READ DEFECT LIST CDB   
126
Table 742...............READ DEFECT LIST Defect List Formats   
127
Table 743............................READ DEFECT LIST Header   
128
Table 744..READ DEFECT LIST Defect Descriptor(s), Bytes from
Index Format..............................................129
Table 745....READ DEFECT LIST Defect Descriptor(s), Physical
Sector Format.............................................130
Table 746......................................READ LONG CDB   
133
Table 747.................................REASSIGN BLOCK CDB   
134
Table 748..................REASSIGN BLOCK Defect List Header   
135
Table 749................REASSIGN BLOCK Defect Descriptor(s)   
136
Table 750.....................RECEIVE DIAGNOSTIC RESULTS CDB   
137
Table 751...................................RELEASE UNIT CDB   
139
Table 752..................................REQUEST SENSE CDB   
142
Table 753..........................REQUEST SENSE Sense Codes   
143
Table 754......................REQUEST SENSE Sense Key Codes   
145
Table 755..........................REQUEST SENSE Sense Codes   
148





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                            TABLES

Table 756...................................RESERVE UNIT CDB   
152
Table 757....................................REZERO UNIT CDB   
153
Table 758...........................................SEEK CDB   
154
Table 759................................SEEK (EXTENDED) CDB   
157
Table 760................................SEND DIAGNOSTIC CDB   
158
Table 761................................START/STOP UNIT CDB   
160
Table 762................................TEST UNIT READY CDB   
162
Table 763.........................................VERIFY CDB   
163
Table 764..........................................WRITE CDB   
165
Table 765...............................WRITE (EXTENDED) CDB   
167
Table 766...............................WRITE AND VERIFY CDB   
169
Table 767...................................WRITE BUFFER CDB   
172
Table 768...........................WRITE BUFFER Data Format   
173
Table 769.....................................WRITE LONG CDB   
175

 LXT-200S Family Product Specification & OEM Technical Manual
 LXT-200S Family Product Specification & OEM Technical Manual

       

 LXT-200S Family Product Specification & OEM Technical Manual


1.0  DISK DRIVE DESCRIPTION

       The LXT-200S disk drives are high capacity, high
       performance, random access storage devices which use
       nonremovable 3.5-inch disks as storage media.  Each
       disk surface employs one moveable head to access the
       data tracks.  See Figure 11, LXT-200S Disk Drive.  The
       total formatted capacity of each drive is 207 megabytes
       at 512 bytes per sector.  The unformatted capacity is
       234 megabytes.


                               

                          Figure 11
                     LXT-200S Disk Drive


       These disk  drives include  the Small  Computer  System
       Interface  (SCSI)  controller  embedded  in  the  drive
       electronics.   An  embedded  Advanced  Technology  (AT)
       controller version,  the LXT-200A,  is also  available.
       Some of  the resulting benefits of having an integrated
       controller  include   the  elimination  of  a  separate
       controller printed  circuit board  (PCB), reduction  in
       the number of associated cables, and elimination of the
       controller-specific power supply.

       High performance  is achieved  through  the  use  of  a
       rotary voice  coil actuator  and a  closed  loop  servo
       system using a dedicated servo surface.  The innovative
       MAXTORQ   rotary    voice   coil   actuator   provides
       performance usually  achieved only  with larger, higher
       powered linear actuators.  The closed loop servo system
       and dedicated  servo surface combine to allow state-of-
       the-art  recording  densities  in  a  3.5-inch  package
       (1,591 tracks per inch, 28,910 bits per inch).

       High capacity  is achieved by a balanced combination of
       high areal  recording density, run-length limited (RLL)
       data encoding  techniques, and  high density  packaging
       techniques.  A three-zone implementation of 1,7 code is
       used. Maxtor's  advanced MAXPAK  electronic  packaging
       techniques use  miniature  surface-mounted  devices  to
       allow all  electronic circuitry  to  fit  on  one  PCB.
       Advanced flexures  and heads  allow closer  spacing  of
       disks, and  therefore allow a higher number of disks in
       a  3.5-inch   package.     Maxtor's  integrated   drive
       motor/spindle design allows a deeper head disk assembly
       (HDA) casting than conventional designs, permitting the
       use of four disks.

 LXT-200S Family Product Specification & OEM Technical Manual


       The drive's electrical interface is compatible with the
       ANSI SCSI standard X3.131-1986, plus the Common Command
       Set (CCS)  requirements.   Size and mounting conform to
       the industry  standard 3.5-inch  form factor for floppy
       and Winchester  disk drives,  and uses  the same direct
       current (DC) voltages and connectors.

       Some key disk drive features include:

       FEATURE                      BENEFITS

         Storage capacity  of 207  Maximum  storage   in  the
          megabytes, formatted  at  3.5-inch    disk     drive
          512  bytes/sector   (234  market; good  upgrade  for
          megabytes, unformatted)   the 5.25-inch  disk drives
                                    which have  less than  200
                                    megabytes of capacity

         Single PCB                High reliability,  ease of
                                    maintenance

         Rotary    voice     coil  Fast,    accurate     head
          actuator and  close loop  positioning
          servo system

         Separate          16-bit  Fast access times, precise
          microprocessor-con-       motor speed  control, high
          trolled    servo     and  reliability,   and    high
          spindle motor             density package

         Thin film metallic media  Higher  bit   density  and
                                    resolution, plus  improved
                                    durability

         Brushless   DC   spindle  Maximum storage capacity
          motor inside hub

         Industry   standard   DC  No AC power required, ease
          power     supply     re-  of integration
          quirements

         Industry        standard  Ease of integration
          physical    size     and
          mounting

         No sway space required    Ease  of   integration  of
                                    system design

         Available   with   5.25-  Ease of  integration  into
          inch, half-high mounting  existing cabinets
          hardware (optional)

 LXT-200S Family Product Specification & OEM Technical Manual


       FEATURE                      BENEFITS
         Low 40  decibels audible  Ideal      for      office
          noise                     environments

         Low   11   watts   power  Less current  requirements
          dissipation               of the  power supply;  low
                                    power use

         Sealed enclosure          Enhanced           thermal
                                    performance:  altitude and
                                    environmental immunity.

       Some key controller features include:

       FEATURE                      BENEFITS

         Sophisticated, hardware-  Minimum time  on SCSI bus;
          based  control  of  SCSI  maximum bus use
          protocol

         Up to  3  megabytes  per  Maximum SCSI bus use
          second   transfer   rate
          asynchronous,   and    6
          megabytes   per   second
          synchronous.

         High performance  buffer  Simultaneous          data
          manager                   transfers  from   disk  to
                                    buffer   and   buffer   to
                                    initiator

         In-line sector sparing    Maintains high performance
                                    over life  of drive,  even
                                    after             numerous
                                    reassignments

         Self-test diagnostics     Ensures reliability of the
                                    drive

         Microcode  down-loadable  Ease of changing SCSI code
          through  SCSI   or   via
          serial port

         Microcode    up-loadable  Flexibility     in     the
          from the  disk drive via  offering of  firmware  im-
          the "soft-boot" routine   plementations

         Very      low       (600  High    throughput     and
          microseconds)       SCSI  performance
          command overhead

         32    kilobytes    cache  Maintains maximum SCSI bus
          buffer                    transfer rate

 LXT-200S Family Product Specification & OEM Technical Manual


       FEATURE                      BENEFITS
         Dedicated         16-bit  SCSI  bus   unaffected  by
          microprocessor for SCSI   drive interface functions,
                                    such as SEEK

         Error map on disk         Automatic           defect
                                    deallocation        during
                                    format; no manual entry

         ANSI  SCSI   2  standard  Compatibility;   ease   of
          X3.131-1986 conformance   integration

         Full  implementation  of  Availability  of   options
          CCS revision 4B           and industry compatibility

         Programmable   56    bit  High data integrity
          error  correction   code
          (ECC).

         Programmable   automatic  Flexibility and  high data
          retry on  SEEK and  READ  integrity
          errors

         Interleave    of     1:1  Maximum data throughput
          supported

         Full                      Optimum      SCSI      bus
          disconnect/reconnect      performance
          capability

         Sector             sizes  User  flexibility;  system
          programmable from 180 to  compatibility
          4,096  bytes.    Today's
          async     drive     only
          supports 512,  1,024 and
          2,048 sector sizes.

       The commands  supported by  the drive  are  listed  and
       discussed later  in this  manual in  Chapter 7.0,  SCSI
       Command Descriptions.   For more information on Group 0
       and Group 1 commands for direct-access devices, see the
       reference documents below:

         ANSI X3.131-1986,  SCSI, American National Standards
          Institute, Inc., June 23, 1986.

         X3T9.2/85-52 Rev  4.B  CCS  of  the  SCSI,  American
          National Standards Institute, Inc., June 23, 1986.



1.1  PRODUCT SPECIFICATIONS

       Product   Specifications   includes   specifications   for
       performance,  function,   environmental  limits,  physical
       dimensions,  reliability,   error  rates,   and  DC  power
       requirements.   At the end of this subchapter is a list of
       the standards and regulations that apply to this family of
       disk drives.


1.1.1     Performance Specifications


                                

                            Table 11
                   Performance Specifications



                                

                       Table 11 (cont'd)
                   Performance Specifications



1.1.2     Functional Specifications


                                

                            Table 12
                    Functional Specifications



1.1.3     Environmental Specifications


                                

                            Table 13
                      Environmental Limits
1.1.4     Physical Specifications


                                

                            Table 14
                       Physical Dimensions



1.1.5     Reliability Specifications


                                

                            Table 15
                   Reliability Specifications



1.1.6     Error Rates


                                

                            Table 16
                           Error Rates



1.1.7     DC Power Requirements


                                

                            Table 17
                      DC Power Requirements



1.1.8     Standards and Regulations

       The Maxtor  LXT-200S disk  drives  satisfy  the  following
       standards and regulations:

       UNDERWRITERS LABORATORIES (UL) is United States safety; UL
       478, Standard  for Safety, Electronic Processing Units and
       Systems.

       CANADIAN STANDARDS  ASSOCIATION (CSA)  is Canadian safety;
       CSA  C22.2  No.  220,  1986,  Information  Processing  and
       Business Equipment (Consumer and Commercial Products).
       VERBAND DEUTSCHER ELECTROTECHNIKER (VDE) is German safety;
       VDE 0806/8.81,  Safety of  Office Appliances  and Business
       Equipment.

       INTERNATIONAL   ELECTROTECHNICAL   COMMISSION   (IEC)   is
       International safety  commission; IEC  950 (formerly 380),
       Safety of Information Technology Equipment.

       CAUTION:     This  equipment   generates  and  uses  radio
       frequency energy,  and may cause interference to radio and
       television reception  if not  installed and used in strict
       accordance with the instructions in this manual.

       The drive  has been  tested and  found to  comply with the
       limits for  a Class B computing device, in accordance with
       the specifications  in Subpart  J of Part 15 of FCC Rules,
       which  are   designed  to  provide  reasonable  protection
       against radio  and television  reception interference in a
       residential installation.   However, there is no guarantee
       that  interference   will  not   occur  in   a  particular
       installation.   If this  equipment does cause interference
       to radio  or television reception, which can be determined
       by  turning   the  equipment  off  and  on,  the  user  is
       encouraged to try to correct the interference using one or
       more of the following measures:

         reorient the receiving antenna
         reorient the computer with respect to the receiver
         move the computer away from the receiver
         plug the  computer into a different outlet, so that the
         computer and receiver are on different branch circuits

       If  necessary,  consult  the  dealer,  or  an  experienced
       radio/television technician,  for additional  suggestions.
       You may  find the  FCC booklet How to Identify and Resolve
       Radio TV  Interference Problems  helpful.  This booklet is
       available  from  the  United  States  Government  Printing
       Office, Washington,  D.C., 20402,  stock  number  004-000-
       00345-4.

       Maxtor is  not responsible  for any  radio  or  television
       interference caused  by unauthorized  modifications to the
       drive.   It is  the responsibility  of the user to correct
       such interference.


1.2  MAJOR PARTS

       The major  elements of  the disk drive are the air filter,
       the head  amplifier, the positioning motor, the read/write
       head assembly,  and the  spindle motor.   See  Figure 11,
       LXT-200S Disk  Drive.  A brief discussion of some of these
       parts appears below, in alphabetical order.
1.2.1     Air Filtration System

       The disks  and read/write  heads are  assembled in a Class
       100 environment  and then  sealed within the HDA.  The HDA
       contains an  absolute filter,  mounted inside the casting,
       to provide  constant internal  air filtration.  See Figure
       12, Air Filtration System.


                                

                           Figure 12
                      Air Filtration System



1.2.2     Drive Mechanism

       The HDA  is a sealed subassembly containing the mechanical
       portion of  the disk  drive.   A brushless  DC disk  drive
       motor contained within the spindle hub rotates the spindle
       and is  controlled by  a dedicated  microprocessor.  Shock
       mounting is  provided internally  in the  HDA to  minimize
       transmission of vibration through the frame.  The frame is
       the mechanical assembly holding the HDA and PCB.


1.2.3     Head Positioning Mechanism

       The read/write  heads are  mounted on a head/arm assembly,
       which is  then mounted  on a ball bearing supported shaft.
       See Figure  13, Head  Positioning Mechanism.   The  voice
       coil, an  integral part  of the  head/arm  assembly,  lies
       inside the  magnet housing  when  installed  in  the  disk
       drive.   Current from  the power  amplifier, controlled by
       the servo  system, induces  a magnetic  field in the voice
       coil which  either aids  or opposes  the field  around the
       permanent magnets.  This reaction causes the voice coil to
       move within  the  magnetic  field.    Since  the  head/arm
       assemblies are connected to the voice coil, the voice coil
       movement is transferred, through the pivot point, directly
       to the heads, to position them over the desired cylinder.


                                

                           Figure 13
                   Head Positioning Mechanism
       Actuator movement  is controlled  by  the  servo  feedback
       signal from  the servo  head.   The servo  information  is
       prewritten at the factory, and is used as a control signal
       for the  actuator to provide track crossing signals during
       a  seek  operation,  track  following  signals  during  on
       cylinder operation,  and timing information, such as index
       and servo  clock.  The servo information also provides the
       timing to  divide a  track  into  sectors  used  for  data
       storage.    The  servo  control  system  has  a  dedicated
       microprocessor for fast, optimized performance.


1.2.4     Read/Write Heads and Disks

       The disk  drive employs  state  of  the  art  sliders  and
       flexures.   The configuration  of the sliders and flexures
       provides   improved    aerodynamic   stability,   superior
       head/disk compliance, and a higher signal-to-noise ratio.

       The disk  media uses  a nickel-cobalt  metallic film  that
       yields high  amplitude signals,  and very  high resolution
       performance, compared  to conventional oxide coated media.
       It also  provides a  highly abrasion  and impact resistant
       surface, decreasing  the potential  for damage  caused  by
       shipping shock and vibration.

       Data  on  each  of  the  data  surfaces  is  read  by  one
       read/write head;  each head accesses 1,314 user accessible
       cylinders.   There  is  one  surface  dedicated  to  servo
       information in each disk drive.
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2.0  DISK DRIVE SETUP

       Jumper locations are identified in Figure 21, PCB Layout.


                                

                           Figure 21
                           PCB Layout



2.1  SCSI ID SELECTION

       SCSI ID  jumpers (pins  one through  six) are  provided to
       configure each disk drive with a SCSI device ID for use in
       multiple SCSI device configurations.

       Table 21,  SCSI ID  Jumpers, is a reference table for the
       SCSI ID  jumper configuration, the ID, and the priority on
       the SCSI bus.  An ID of seven is the highest priority in a
       multiple device configuration, and is usually used for the
       initiator.


                                

                            Table 21
                         SCSI ID Jumpers


       The disk  drive is  shipped from the factory with an ID of
       six.   This assures  that sufficient jumpers are available
       for any  address except  seven, which  is usually reserved
       for the host system.


2.2  DRIVE POWER-UP OPTIONS


                                

                            Table 22
                   Summary of Power-Up Options


       Wait for  START Command:  With no jumper on pins seven and
       eight of  J6, the  disk drive  does not  spin up until the
       initiator issues  a START/STOP UNIT command with the start
       bit equal to one.

       Start When Power Is Applied:  When pins seven and eight of
       J6 are  jumpered, the  motor starts  as soon  as power  is
       applied.  The disk drive is shipped in this configuration.



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2.3  TERMINATOR POWER SELECTION

       Power to the terminators may come internally from the disk
       drive, or externally from the SCSI bus.

       The drive  electronics are  capable of sensing if the host
       is providing the power to the terminators.  If the host is
       not providing  the power then the disk drive automatically
       provides the power to the terminators.


2.4  PARITY DISABLE OPTION

       The parity  disable jumper,  pins  nine  and  ten  of  J6,
       enables (in) or disables (out) odd parity detection in the
       disk drive.   Currently, odd parity is always generated by
       the disk drive and provided to the SCSI bus.

       The disk  drive is  shipped with  pins nine  and  ten  in,
       enabling parity detection.


2.5  SECTOR SIZE

       The disk  drive is shipped from the factory formatted with
       512-byte sectors.   Configuration  parameters are  default
       values in  all optional  cases.   It is  recommended  that
       users reformat  the drive  with the  user's  sector  size,
       using the P list, and the user's configuration parameters.


2.6  INTERFACE TERMINATION

       SCSI devices  require proper  interface termination.   The
       first device and the last device on a SCSI bus daisy chain
       must  be   terminated.    See  Figure  51,  Typical  SCSI
       Configurations.   Remove the  terminators from any devices
       in between.   For  instance, if  a disk  drive is  in  the
       middle of  a SCSI bus daisy chain, remove its terminators.
       The drive terminators are shown in Figure 21, PCB Layout.

       Terminator pin  one is marked with a dot on the terminator
       as shown  in Figure 21, PCB Layout.  The terminators (U40
       through U42)  all look  like the  side view  inset in  the
       figure.   The orientation  of the terminator on the PCB is
       also shown.   Note  that the PCB's hole/solder pad for pin
       one has a square outline, whereas all the other holes/pads
       have a  round outline.   Also, note that pin one is always
       the closest pin to the power connector, J3.

       NOTE: All terminator  packs  (U40  through  U42)  must  be
       oriented with  the dot  towards J3  for the  disk drive to
       work properly.




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       As shipped, the interface signal lines are terminated with
       three removable 220/330 ohm resistor network packs.

       The devices  driving the  disk drive inputs should be open
       collector devices capable of sinking at least 48 milliamps
       at a  voltage level  of less  than 0.5  volts DC  (7438 or
       equivalent).

       Devices receiving  the disk  drive outputs  should  be  of
       SCHMITT trigger  type to  improve noise  immunity (74LS14,
       74LS240, or  equivalent).   The initiator  should not load
       the bus  with more  than one  standard low  power  Schotky
       transistor-transistor logic  (LSTTL) input  load per line,
       and  should   terminate  all   signals  with  220/330  ohm
       terminators.


2.7  SERVICE CONNECTOR

       Connector J4  in Figure  22, Connector  Locations,  Front
       View of  Drive, is  a service  connector providing the RS-
       232, the synchronous spindle, and the ability to carry the
       LED signal  beyond the  disk drive.  The RS-232 is used to
       port new  firmware updates  to the  disk.  The synchronous
       spindle option  is currently  not supported.   The service
       connector is  a ten-pin  part.   The mating connector is a
       Berg 6976410 part.


                                

                           Figure 22
            Connector Locations, Front View of Drive


       Pin assignments  are shown in Table 23, Service Connector
       Pin Assignments (also see Figure 52, Connector Locations,
       Rear View of Drive).


                                

                            Table 23
                Service Connector Pin Assignments


       When an  LED is connected to pin nine (+) and pin ten (-),
       that LED  functions in the same manner as the LED which is
       mounted on  the disk drive's faceplate.  This is typically
       used in  cases when  the drive  is mounted  in a  position
       where the LED is not visible and the faceplate is removed.

       Pins two  through four  are the  RS-232 lines used to down
       load firmware updates to the microprocessor which are then



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       stored on  the disk.   Pins three (transmit data) and four
       (receive data)  are the main communication lines.  Pin two
       is used  to debug  the processor  and for  a  non-maskable
       interrupt.   Pins five  and six  are signal  ground lines.
       Pin eight  will be  used at  a later date to implement the
       synchronous spindles.


2.8  SPINDLE SYNCHRONIZATION CONTROL

       

       Spindle synchronization  is not  currently available,  but
       this feature,  when implemented,  will allow  a number  of
       Maxtor LXT-200S  disk drives to synchronize the rotational
       position of  their  spindles.    The  pin  assignment  for
       connector J4,  which will  be used  for this  feature,  is
       shown in Table 23, Service Connector Pin Assignments, Pin
       8.






































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3.0  DISK DRIVE INSTALLATION

       This chapter  includes the information you need to install
       the  disk   drive,  specifically   mounting  and  shipping
       considerations.


3.1  MOUNTING

       The disk  drive may  be mounted  in any  position.  In any
       final mounting configuration, ensure that the operation of
       the three  shock mounts,  which isolate  the HDA  from the
       frame,  are  not  restricted.    Certain  switching  power
       supplies may  emanate electrical  noise, which can degrade
       the specified  read error  rate.  For best results, orient
       the drive  so that  the PCB  assembly is  not adjacent  to
       these noise sources.

       Twelve mounting holes, four on the bottom and four on each
       side, are  provided for  mounting the  disk drive  into an
       enclosure.  The size and location of these holes, shown in
       Figure 31, Mechanical Outline, Bottom and Side Views, are
       identical to  industry standards.   Overall height, width,
       and depth,  along with  other key dimensions, are shown in
       Figure 31, and Figure 32, Mechanical Outline, Isometric.

       CAUTION:     The  casting  is  very  close  to  the  frame
       mounting holes  in some locations.  Mounting screw lengths
       must be  chosen so  that no  more than  0.125 inch  of the
       screw is  available to enter the frame mounting hole.  The
       torque applied  to the mounting screws should be between 9
       and 12 inch-pounds.


                                

                           Figure 31
             Mechanical Outline, Top and Side Views



                                

                           Figure 32
               Mechanical Outline, Isometric View


       The faceplate  is clipped  on to  the front of the HDA and
       may be  removed in installations that require it.  Lift up
       on the faceplate clips and unplug the light-emitting diode
       (LED)  cable  from  the  PCB,  as  shown  in  Figure  33,
       Removable Faceplate.





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                           Figure 33
                       Removable Faceplate



3.2  POWER-UP TESTING

       The following  information  is  based  on  the  ANSI  SCSI
       standard  (X3.131-1986),   and  the   CCS.      For   more
       information, refer to these publications.

       This section describes the sequence of events during drive
       self-test and  initialization sequences.    The  self-test
       sequence is  performed upon  power up,  and is followed by
       the initialization  sequence.   When the  drive is  reset,
       either by  the SCSI  bus -RST  signal or by the BUS DEVICE
       RESET  message,   only  the   initialization  sequence  is
       performed.

       NOTE: The self-test sequence can also be initiated via the
       SEND DIAGNOSTIC  and RECEIVE  DIAGNOSTIC RESULTS commands,
       and these  commands include options for more comprehensive
       diagnostics.


3.2.1     Self-Test Sequence

       The self-test  sequence is  executed upon disk drive power
       up.   The self-test sequence verifies the integrity of the
       hardware.    This  test  is  not  an  exhaustive  hardware
       diagnostic, but  simply checks  the major  components  for
       full functionality.   The  drive does  not  respond  to  a
       SELECTION phase  on the  SCSI bus  for about the first 250
       milliseconds of  the self-test.   After  250  milliseconds
       have passed,  the drive  responds to SELECTION with a BUSY
       status for  2 to  3 seconds: this time is spent completing
       the remaining  self-test sequences,  initializing the SCSI
       chip, and  enabling the  SCSI interrupts.  After the self-
       test is  complete and  the SCSI  circuitry is  initialized
       (approximately 3 seconds), the drive responds to SELECTION
       with CHECK CONDITION status and the appropriate sense data
       (i.e., UNIT ATTENTION, POWER ON/RESET condition).

       The self-test sequence consists of the following events:

         Hardware  Reset   Test  -   This  routine   tests   the
         microprocessor, buffer  controller, disk  formatter, and
         SCSI reset  latch for the proper power up condition.  If
         any of  these tests  fail, the  disk drive  can only  be
         reset by a POWER UP condition.





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         Microprocessor  Test   -   This   routine   tests   the
         microprocessor's internal  memory, timers,  and register
         bank switching for proper operation.

         Buffer Controller  Test - This routine tests the buffer
         controller for  proper operation.  All the registers are
         tested and  the chip  is engaged to access random-access
         memory (RAM).

         Disk Formatter  Test -  This  routine  tests  the  disk
         formatter chip  by  writing  and  reading  all  possible
         patterns to  each of  the disk formatter chip registers.
         After the  registers  are  tested,  the  interrupts  are
         tested to  ensure that  the formatter  chip generates an
         interrupt when a command completes.

         SCSI Controller  Test -  This routine  tests  the  SCSI
         controller  chip   by  executing   the  chip  diagnostic
         command.   After  the  diagnostic  test  completes,  the
         interrupts are  tested to  ensure  that  the  SCSI  chip
         generates  an   interrupt  when   a  command  completes.
         Finally, the registers are tested by writing and reading
         all possible  patterns to  each of  the SCSI  controller
         chip registers.

       If any portion of the self-test fails, except the hardware
       reset test,  the disk  drive can  be reset  by a  SCSI bus
       RESET condition  or a  power  up  RESET  condition.    The
       failure  of  the  hardware  reset  test  is  considered  a
       catastrophic failure  and the controller can only be reset
       from such a failure by a power up RESET condition.


3.2.2     Initialization Sequence

       The initialization sequence is executed for any one of the
       following three reasons:

         a POWER UP condition occurs
         the SCSI bus -RST signal is asserted
         a BUS  DEVICE  RESET  message  (on  the  SCSI  bus)  is
       received

       After a  successful initialization, the first command from
       each initiator  is terminated  with a  CHECK CONDITION and
       POWER ON/RESET sense code of 29h.

       Until the disk drive has been spun up, any command sent by
       an  initiator  which  requires  a  ready  drive  for  GOOD
       completion status,  is terminated  with a CHECK status and
       DRIVE NOT  READY sense  key.   Commands that  may complete
       with GOOD  status prior  to  the  drive  being  ready  are
       REQUEST SENSE,  INQUIRY,  START/STOP  UNIT,  READ  BUFFER,
       WRITE BUFFER, and REZERO.



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       After the  disk drive  has spun up, the first command sent
       by the  initiator which accesses the media, loads the MODE
       SENSE parameters.   An  initiator should  not request  any
       MODE SENSE parameters until the drive is ready.


3.2.3     Self-Configuration

       When the  disk drive  powers up or is reset, it configures
       itself from  the parameters  and information  saved on the
       drive from  the previous  format operation.  This includes
       the drive's  exact model  number returned  in the  INQUIRY
       command and  the MODE  SELECT parameters  in the  pages of
       parameters.   Refer to  section 7.4, MODE SELECT, and sec-
       tion 7.5,  MODE SENSE later in this manual, which describe
       the parameters in the pages.


3.2.4     UNIT ATTENTION Condition

       A UNIT  ATTENTION condition  is created for each initiator
       whenever the  disk drive  has been  reset (by a BUS DEVICE
       RESET message  or a  RESET condition),  or when  the  MODE
       SELECT parameters  have been  changed by other initiators.
       The UNIT  ATTENTION condition  (sense key 06h) is returned
       in the  sense data  by the  drive in response to the CHECK
       CONDITION (02h) status byte.  The UNIT ATTENTION condition
       persists for  each initiator  until that  initiator issues
       any command other than INQUIRY.

       If an INQUIRY command is received from an initiator with a
       pending UNIT  ATTENTION condition  (before the  disk drive
       reports CHECK  CONDITION status),  then the  drive reports
       any pending  sense data  and preserves  the UNIT ATTENTION
       condition.

       If a  REQUEST SENSE  command is received from an initiator
       with a  pending UNIT  ATTENTION condition (before the disk
       drive reports  CHECK CONDITION  status),  then  the  drive
       reports any  pending sense  data and  preserves  the  UNIT
       ATTENTION condition in the sense data.  However, the CHECK
       CONDITION is  cleared, and thus GOOD status is returned on
       a subsequent command, which then clears the UNIT ATTENTION
       from the sense data.


3.2.5     Buffering Scheme

       The disk drive buffer is a 32-kilobyte FIFO buffer.  There
       are 32,767  bytes available  for data storage.  The buffer
       controller allows  transfer  to  the  disk  and  from  the
       initiator simultaneously,  or from  the disk  and  to  the
       initiator simultaneously.




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3.3  SHIPPING

       At power down, the heads are automatically positioned over
       the nondata,  dedicated landing zone on each disk surface.
       The automatic  shipping lock  solenoid is  also engaged at
       this time.   Maxtor  ships the  disk drive  in single- and
       multipack shipping  containers.   Users can ship the drive
       installed when the nonoperating shock and vibration limits
       are not exceeded.
















































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4.0  DISK DRIVE DAILY OPERATION

       The  disk  drive  consists  of  read/write,  control,  and
       interface electronics,  read/write heads,  a servo head, a
       head positioning  actuator, a  disk  drive  motor/spindle,
       media, and  an air  filtration  system.    The  components
       perform the following functions:

         interpret and generate control signals
         position the heads over the desired track
         read and write data
         provide automatic error correction to the data
         provide a contamination-free environment
         provide a controller to interact with the initiator
         maintain precise spindle rotation speed


4.1  READ/WRITE CONTROL AND SCSI CONTROLLER ELECTRONICS

       All of  the disk  drive  and  controller  electronics  are
       packaged on  a single PCB.  This PCB, which includes three
       microprocessors,  performs   the  following   disk   drive
       functions:

         data separation
         reading/writing of data
         index detection
         head positioning
         head selection
         disk drive selection
         fault detection
         recalibration on power up
         track position counter
         power and speed control for spindle disk drive motor
         disk drive up-to-speed indication
         monitoring for WRITE FAULT conditions
         control of all internal timing

       The PCB performs the following controller functions:

         error detection and correction
         SCSI bus disconnect/reconnect functions
         SCSI bus arbitration
         defect handling
         data transfer
         automatic retries
         data buffering
         command linking
         sector formatting








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4.2  TRACK AND SECTOR FORMAT

       The standard  track format is organized into numbered data
       segments, or  sectors.  See Figure 41, Track Format.  The
       sectors are  addressed via the logical block address (LBA)
       in the SCSI commands.  The method of encoding is 1,7 code.


                                

                           Figure 41
                          Track Format













































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5.0  INTERFACE

       This is the first of three chapters on the SCSI interface.
       This chapter includes information on the logical interface
       and the electrical power interface.


5.1  SCSI INTERFACE

       This  section  includes  information  on  initiator-target
       configurations, signal  definitions, pin  assignments, and
       the connector.


5.1.1     Initiator-Target Configurations

       The SCSI  initiator interface  offers a  number of  unique
       advantages which  facilitate the  interconnection  of  the
       disk drive  with one  (or more)  computer systems.  Unlike
       traditional microcomputer  disk interfaces, such as ST506,
       SCSI   supports   multiple   peripherals   and   different
       peripheral types, all operating on the same bus structure.
       Figure 51, Typical SCSI Configurations, shows examples of
       typical configurations.


                                

                           Figure 51
                   Typical SCSI Configurations


       The  disk   drive   also   supports   multiple   initiator
       configurations consistent with the established arbitration
       cycle outlined  in  the  SCSI  standards.    Configuration
       changes are  made by  SCSI address  jumpers, which are set
       when the drive is installed in the system (jumper settings
       are discussed in Chapter 2.0, Disk Drive Setup, earlier in
       this manual).

       The SCSI implementation used in the disk drive is intended
       to  facilitate   high-speed  data   transfer  between  the
       initiator and  the drive.    Interconnection  between  the
       initiator system(s)  and the  drive  is  via  a  fifty-pin
       ribbon cable, and uses the single-ended alternative, which
       allows up to 6 meters of cable length.


5.1.2     Logical/Electrical Signal Definitions

       The SCSI  bus uses eighteen signals.  Nine signals are for
       the 8-bit  data bus,  with one  data parity bit; the other
       nine signals  are the SCSI control lines, which coordinate
       bus accesses  for transfers of commands, data, status, and



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       messages.   The interface  signals are listed below; refer
       to the SCSI standard for further details.  Pin assignments
       of the  connector  are  provided  in  section  5.1.3,  Pin
       Assignments and Connector, later in this chapter.

       Across the  SCSI bus  all initiator  signals are low-true.
       The signals are asserted, or active, at 0 to 0.8 volts DC,
       and negated,  or inactive,  at 2.5 to 5.25 volts DC.  This
       low-true logic  is indicated  by the  negative sign  which
       precedes the signal name.

       -RST
       The -RST  (reset) signal  is an or-tied signal asserted by
       the initiator,  causing the  disk drive  to  do  a  "hard"
       RESET, self  configure and  return to  the IDLE condition.
       This signal  is normally  used during a power-up sequence.
       The -RST pulse should be at least 25 microseconds wide.

       -SEL
       The -SEL  (select) signal  is asserted  by the  initiator,
       along with  the disk  drive's SCSI  ID bit  (zero  through
       seven), causing  the drive  to be selected.  The -SEL line
       must be  negated by  the initiator after the drive asserts
       the -BSY  line in  response to  a proper  selection.   The
       signal can  be asserted  by the arbiter (initiator or disk
       drive) in  the ARBITRATION  phase.   The  signal  is  also
       asserted by the drive during the RESELECTION phase.

       -BSY
       The -BSY  (busy) signal  is an  or-tied signal asserted by
       the disk drive, indicating that the bus is being used.  It
       is also  asserted by  the arbiter  during the  ARBITRATION
       phase and  by the  initiator  and  the  drive  during  the
       RESELECTION phase.

       -C/D
       Assertion of  the -C/D  (control/data) signal  by the disk
       drive  indicates   that  command,   status,   or   message
       information  is   to  be  transferred  on  the  data  bus.
       Negation of  this  line  indicates  that  data  is  to  be
       transferred on the data bus.

       -I/O
       When the  -I/O (input/output)  signal is  asserted by  the
       disk drive it indicates that information is transferred to
       the initiator  from the  drive.   Negation of  the  signal
       indicates that  information is  transferred to  the  drive
       from the  initiator.    Note  that  IN  means  toward  the
       initiator.

       -REQ
       When asserted by the disk drive, the -REQ (request) signal
       indicates that  a byte  is to  be transferred  on the data




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       bus.  -REQ is negated following assertion of the -ACK line
       by the initiator.

       -ACK
       The  -ACK   (acknowledge)  signal   is  asserted   by  the
       initiator,  following  assertion  of  the  -REQ  line,  to
       indicate data  has been accepted by the initiator, or that
       data is  ready to be transferred from the initiator to the
       disk drive.   -ACK  is negated  following negation  of the
       -REQ line.

       -ATN
       The -ATN  (attention) signal  is asserted by the initiator
       to indicate the ATTENTION condition, which is a request by
       the initiator  for the disk drive to enter the MESSAGE OUT
       phase.

       -MSG
       The -MSG  (message) signal  is asserted  by the disk drive
       during one  of the message phases.  Messages may be either
       IN or OUT, depending on the state of the -I/O signal.

       -DB (7-0, P)
       The eight bidirectional data bus lines (DB 7-0) and parity
       line (DBP)  are used  to  transfer  8  bit  parallel  data
       to/from the  initiator.  Bit seven is the most significant
       bit.   Bits zero  through seven  are also  used as SCSI ID
       bits during  the ARBITRATION,  SELECTION  and  RESELECTION
       phases.  Data bus parity (DBP) is odd.


5.1.3     Pin Assignments and Connector

       The disk drive communicates with an initiator system via a
       fifty-pin   connector,   J1.      The   logical/electrical
       configuration of the SCSI connector is given in Table 51,
       Connector Pin  Assignments.   Note that the minus sign (-)
       indicates low-true  logic, and  that all odd-numbered pins
       are return  (ground) pins for the associated even-numbered
       pins, except  for pin twenty-five, which is not connected.
       Pin one  is located  on the  end of  J1 closest  to the DC
       power connector, J3.  See Figure 52, Connector Locations,
       Rear View of Drive.


                                

                            Table 51
                    Connector Pin Assignments








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                           Figure 52
             Connector Locations, Rear View of Drive


       Connection to  J1 is  via  a  nonshielded  fifty-conductor
       connector, consisting  of two  rows of  twenty-five female
       contacts on  0.1 inch  centers.   Figure 53,  SCSI  Cable
       Connector, shows  the configuration  and dimensions  of  a
       suitable  mating  connector.    Recommended  strain-relief
       connectors are  AMP part number 1-499506-2, or Dupont part
       number 669002  (66900-250).   Use of  a keyed connector is
       strongly recommended.


                                

                           Figure 53
                      SCSI Cable Connector



5.2  ELECTRICAL POWER INTERFACE

       This subsection  describes the  power-up sequence  for the
       disk drive,  and the  two connectors  associated with  the
       electrical power  interface.   These  connectors  are  the
       power connector, J3, and the frame ground connector, J4.


5.2.1     Power-Up Sequence

       DC power  (+5 volts  and +12 volts) may be supplied in any
       order.   Both power  supplies must  be present, and within
       the tolerances  of the  power sensing  circuit, before the
       motor will  spin up.  When the spindle reaches full speed,
       the actuator  lock automatically  disengages.    The  disk
       drive performs  automatic SEEK calibration during start up
       for optimum  SEEK performance.   The  drive spins  up  and
       becomes ready  in 15  seconds.   The  drive  executes  its
       recalibration sequence  whenever power  is applied  or the
       SCSI START/STOP command is invoked via the SCSI bus.


5.2.2     Power Connector

       The DC  power connector,  J3  (shown  in  Figure  54,  J3
       Connector) is  a four-pin  AMP MATE-N-LOCK connector, part
       number 3505430-1.  The recommended mating connector is AMP
       part number 1-480424-0, using AMP pins part number 350078-
       4 (strip)  or part  number 61173-4 (loose piece).  J3 pins
       are numbered  and assigned as shown in Figure 54.  Figure




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       52, Connector  Locations, Rear  View of  Drive, shows the
       location of J3 on the disk drive.


                                

                           Figure 54
                          J3 Connector

















































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6.0  SCSI PHASES

       The condition  on the  SCSI bus  can be divided into eight
       distinct phases:

       BUS FREE phase
       ARBITRATION phase
       SELECTION phase
       RESELECTION phase
       COMMAND phase \
       DATA phase     \  These phases are collectively termed the
       STATUS phase   /  Information Transfer phases.
       MESSAGE phase /

       The various  phases are  defined by  the state of the SCSI
       bus signals  -SEL, -BSY, -MSG, -C/D, -I/O, -REQ, and -ACK.
       The SCSI  bus can  never be  in more  than one  phase at a
       time.   Figure 61, Signal Sequence Chart for SCSI Phases,
       shows the signal sequence of the eight phases.  The figure
       has been  provided for  your reference  while reading  the
       following sections.

       NOTE: A new  phase does  not begin until the REQ signal is
       asserted  for the first byte of the new phase.


                                

                            Table 61
                  Signal States and Bus Phases



                                

                           Figure 61
              Signal Sequence Chart for SCSI Phases



6.1  BUS FREE PHASE

       The BUS FREE phase is used to indicate that no SCSI device
       is actively  using the  SCSI bus, and that it is available
       for subsequent  users.  BUS FREE occurs when the drive re-
       leases  -BSY  following  a  RESET  condition,  or  certain
       message phases (that is, COMMAND COMPLETE and DISCONNECT).


6.2  ARBITRATION PHASE

       The ARBITRATION  phase allows  one  SCSI  device  to  gain
       control of  the SCSI bus so that it can assume the role of
       an initiator  or target  (drive).   The arbitrating device



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       waits for  the BUS  FREE phase  to occur.  It then asserts
       its own SCSI ID bit and -BSY.  The arbitrating device then
       examines the  data bus.   If a higher priority SCSI ID bit
       exists on  the data  bus,  the  arbitrating  device  loses
       arbitration  and   releases  -BSY   and  the   data   bus.
       Otherwise, the  arbitrating device  wins  arbitration  and
       asserts -SEL.

       NOTE: Implementation of  the ARBITRATION phase is a system
       option.   Systems that  do not  implement this  option can
       have only  one initiator.   The  ARBITRATION phase  is re-
       quired  for  systems  that  use  the  disconnect/reconnect
       feature.


6.3  SELECTION PHASE

       If the initiator wins arbitration, it enters the SELECTION
       phase by  continuing to  assert its  own initiator SCSI ID
       bit and  asserting the drive's SCSI ID bit.  The initiator
       then  negates   -BSY  (-SEL   remains  asserted   by   the
       initiator).  If the initiator expects the drive to discon-
       nect/reconnect, the  initiator must  assert the  -ATN line
       prior to the negation of -BSY.

       If the  initiator does  not support  arbitration, then the
       SELECTION phase  is entered  from the BUS FREE phase.  The
       initiator asserts only the drive's SCSI ID bit and asserts
       -SEL.

       During the  SELECTION phase, the drive maintains a negated
       -I/O line so that the SELECTION phase may be distinguished
       from the RESELECTION phase.

       The  drive   determines  that  it  has  been  selected  by
       detecting  its  SCSI  ID  bit  asserted  on  the  bus  (as
       determined by  the ID  jumpers-see section  2.1,  SCSI  ID
       Selection, earlier in this manual).

       If more  than two  IDs are  asserted on  the data  bus, or
       parity is  enabled and  bad parity  is detected, the drive
       does not respond to SELECTION.

       The  drive  asserts  -BSY  after  detecting  it  has  been
       selected.   At this  point, the initiator must negate -SEL
       and may remove the IDs from the data bus.


6.4  RESELECTION PHASE

       After disconnecting  to free  the bus  for other activity,
       the drive  reconnects when it is ready to transfer data or
       status across  the bus.   The drive arbitrates for the bus




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       and, if  it wins, reselects the initiator.  RESELECTION is
       very similar  to SELECTION,  except that  the -I/O  signal
       line is  asserted.   The drive asserts its own SCSI ID bit
       and the  SCSI ID  bit of  the  initiator  which  is  being
       reselected.   The drive  releases -BSY  (-BSY was  already
       asserted during arbitration) and continues to assert -SEL.
       The initiator  detects  that  it  has  been  selected  and
       responds by asserting  -BSY.  The drive detects that the -
       BSY signal is now true and responds by also asserting -BSY
       (at this  point, both  the initiator  and  the  drive  are
       holding the  -BSY signal  low).  The drive then releases -
       SEL and  the initiator responds by releasing -BSY (-BSY is
       still being asserted by the drive.  See Figure 61, Signal
       Sequence Chart for SCSI Phases.)

       After  reselecting  the  initiator,  the  drive  sends  an
       IDENTIFY message to identify itself to the initiator.

       If the  initiator does  not  respond  to  the  reselection
       within a selection time-out delay (see Table 62, SCSI Bus
       Timing), the  drive releases the bus and then rearbitrates
       for the  bus, trying  to reselect  the initiator.  It does
       this up  to 255  times, or until the initiator responds or
       the drive is reset.

       NOTE: The  drive   does  not  disconnect  if,  during  the
       SELECTION phase,  the initiator does not set its initiator
       SCSI device  ID on  the bus  and if the initiator does not
       send an  IDENTIFY message  out (with  bit six asserted) to
       the drive.


6.5  INFORMATION TRANSFER PHASES

       The -C/D,  -I/O, and  -MSG signals are used to distinguish
       between  the   different   information   transfer   phases
       (COMMAND, DATA,  STATUS, and MESSAGE).  The drive controls
       these three  signals, and, therefore, controls all changes
       from one  phase to  another.   The initiator can request a
       MESSAGE OUT  phase by  asserting -ATN,  and the  drive can
       cause a  BUS FREE  phase by deasserting -SEL and -BSY (and
       all other SCSI bus signals).

       The information  transfer phases use one or more -REQ/-ACK
       handshakes to  control the  information transfer.   Each -
       REQ/-ACK handshake allows the transfer of 1 byte of infor-
       mation.   During the  information  transfer  phases,  -BSY
       remains true and -SEL remains false.  Additionally, during
       the information  transfer phases,  the drive  continuously
       envelopes the -REQ/-ACK handshake(s) with -C/D, -I/O), and
       -MSG in such a manner that these control signals are valid
       for a  bus settle  delay (see  Table 62, SCSI Bus Timing)
       before the  assertion of  -REQ of the first handshake, and




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       remain valid  until the negation of -ACK at the end of the
       last handshake.


                                

                            Table 62
                         SCSI Bus Timing



6.5.1     Asynchronous Information Transfer

       The drive  controls the  direction of information transfer
       by means of a -I/O signal.  When -I/O is true, information
       is transferred from the drive to the initiator.  When -I/O
       is false, information is transferred from the initiator to
       the drive.

       If -I/O  is true  (transfer to  the initiator),  the drive
       first drives  -DB (7-0, P) to their desired values, delays
       at least  one deskew  delay, plus  a cable skew delay (see
       Table 62,  SCSI Bus  Timing), and then asserts -REQ.  -DB
       (7+0, P)  remains valid  until -ACK  is true at the drive.
       The initiator  reads -DB (7-0, P) after -REQ is true, then
       signals its  acceptance of  the data  by  asserting  -ACK.
       When -ACK  becomes true at the drive, the drive may change
       or release  -DB (7-0,  P) and negates -REQ.  After -REQ is
       false, the  initiator then  negates -ACK.   After  -ACK is
       false, the  drive may  continue the transfer by continuing
       to drive  -DB (7-0,  P) and  asserting -REQ  as  described
       above.

       If -I/O  is false  (transfer  to  the  drive),  the  drive
       requests information  by asserting  -REQ.   The  initiator
       drives -DB  (7-0, P)  to their  desired values,  delays at
       least one deskew delay, plus a cable skew delay (see Table
       62, SCSI  Bus Timing),  and asserts  -ACK.  The initiator
       continues to drive -DB (7-0, P) until -REQ is false.  When
       -ACK becomes  true at the drive, the drive reads -DB (7-0,
       P) and  then negates -REQ.  When -REQ becomes false at the
       initiator, the  initiator may  change or release -DB (7-0,
       P), and negates -ACK.  The drive may continue the transfer
       by asserting -REQ as described above.


6.5.2     Synchronous Data Transfer

       Synchronous data  transfer is  not yet supported.  When it
       is supported,  synchronous data transfer will be optional,
       and may  be used  only if  previously  agreed  to  by  the
       initiator and  drive through  the  message  system.    See
       section 6.6,  SYNCHRONOUS DATA  TRANSFER REQUEST  Message,




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       later in  this chapter.  The messages determine the use of
       synchronous mode  by the  initiator  and  the  drive,  and
       establish a  -REQ/-ACK offset  and a transfer period.  The
       synchronous mode,  once established, remains in effect for
       all DATA  phases until  a RESET  condition or  power cycle
       occurs.

       The -REQ/-ACK  offset specifies the maximum number of -REQ
       pulses that  can be  sent by  the target in advance of the
       number of -ACK pulses received from the initiator, thereby
       establishing a  pacing mechanism.   If  the number of -REQ
       pulses exceeds  the number of -ACK pulses by the -REQ/-ACK
       offset, the drive does not assert -REQ until the next -ACK
       pulse  is   received.     A  requirement   for  successful
       completion of  the DATA  phase is  that the number of -ACK
       and -REQ pulses be equal.

       The drive  asserts the  -REQ signal  for a  minimum of one
       assertion period.  The drive waits at least the greater of
       a transfer  period from  the last  transition of  -REQ  to
       true, or  the minimum  of a  negation period from the last
       transition of -REQ to false before the drive asserts the -
       REQ signal.

       The initiator  sends one pulse of the -ACK signal for each
       -REQ pulse  received.   The  initiator  asserts  the  -ACK
       signal for  a  minimum  of  one  assertion  period.    The
       initiator waits  at least the greater of a transfer period
       from the last transition of -ACK to true, or for a minimum
       of a  negation period  from the last transition of -ACK to
       false, before the initiator asserts the -ACK signal.

       If -I/O  is true  (transfer to  the initiator),  the drive
       first drives  -DB (7-0,  P) to their desired values, waits
       at least  one deskew delay, plus one cable skew delay (see
       Table 62,  SCSI Bus  Timing), and then asserts -REQ.  -DB
       (7+0, P) are held valid for a minimum of one deskew delay,
       plus one  cable skew  delay, plus one hold time (see Table
       62) after  the assertion of -REQ.  The drive asserts -REQ
       for a minimum of one assertion period.  The drive may then
       negate -REQ  and change  or release  -DB (7-0,  P).    The
       initiator reads  the value on -DB (7-0, P) within one hold
       time of  the transition  of -REQ  to true.   The initiator
       then responds with an -ACK pulse.

       If -I/O  is false  (transfer to  the drive), the initiator
       transfers 1  byte for  each -REQ  pulse received.    After
       receiving a -REQ pulse, the initiator first drives -DB (7-
       0, P)  to the  desired values,  delays at least one deskew
       delay, plus  one cable skew delay (see Table 62, SCSI Bus
       Timing) and  then asserts  -ACK.   The initiator holds -DB
       (7-0, P)  valid for  at least  one deskew  delay, plus one
       cable skew delay, plus one hold time (see Table 62) after




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       the assertion  of -ACK.   The initiator asserts -ACK for a
       minimum of  one assertion  period.  The initiator may then
       negate -ACK  and may  change or release -DB (7-0, P).  The
       drive reads the value of -DB (7-0, P) within one hold time
       of the transition of -ACK to true.


6.5.3     COMMAND Phase

       After being  selected and processing the IDENTIFY message,
       if any,  the drive normally switches to the COMMAND phase.
       The  6   or  10  bytes  of  command  information  (command
       descriptor  block,   or  CDB)  are  transferred  from  the
       initiator to the drive.

       If enabled,  parity is  checked on  each command byte.  If
       bad parity is detected, the command is aborted.  The drive
       switches to  the STATUS  phase, returns  a CHECK CONDITION
       status, and  sets the  sense  key/error  code  to  ABORTED
       COMMAND/Parity Error  for that  initiator.  The drive then
       switches to  the MESSAGE phase, returns a COMMAND COMPLETE
       message, and goes to the BUS FREE phase.

       After each command byte transfer, the -ATN bit is checked;
       if set,  the drive  switches to the MESSAGE OUT phase, and
       receives and then acts on the message.


6.5.4     DATA IN and DATA OUT Phases

       In commands  that require  a DATA phase (READ, WRITE, MODE
       SELECT), the  drive enters  a DATA phase.  During the DATA
       IN phase,  data is  transferred  from  the  drive  to  the
       initiator.  During the DATA OUT phase, data is transferred
       from the initiator to the drive.

       If bus  parity is  enabled and bad parity is detected, the
       command is aborted.  The controller switches to the STATUS
       phase, returns  a CHECK  CONDITION status,  and  sets  the
       sense key/error  code to  ABORTED COMMAND/Parity Error for
       that initiator.   The  drive then  switches to the MESSAGE
       phase, returns a COMMAND COMPLETE message, and goes to the
       BUS FREE phase.

       After each  block, or group of blocks, is transferred, the
       -ATN bit  is checked;  if set,  the drive  switches to the
       MESSAGE phase to receive, and then act on, the message.


6.5.5     STATUS Phase

       After   completing    any   command    (successfully    or
       unsuccessfully, as  indicated by  the  status  byte),  the




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       drive switches  to the STATUS phase and returns the status
       byte to  the initiator  (as specified in Table 63, Status
       Byte).   The drive  also switches  to the STATUS phase for
       reporting  a   BUSY,  INTERMEDIATE/GOOD,   or  RESERVATION
       CONFLICT status.   The  drive does  not go  to the  STATUS
       phase if  it is  cleared by  a BUS  DEVICE RESET  or ABORT
       message, or  by a  "hard" RESET  condition.  Following the
       STATUS phase, the drive enters the MESSAGE phase.

       The format  of the  status  byte  containing  the  command
       completion information  is defined  in Table  63,  Status
       Byte.


                                

                            Table 63
                           Status Byte


       The reserved  field, bit  seven, is  set aside  for future
       standardization and is always set to zero.

       The vendor  unique fields,  bits five,  six, and zero, are
       reserved and are always set to zero.

       The status  code field,  bits one through four, is used to
       specify the  status of  the completed command.  Table 64,
       Status Codes,  gives the  bit values  for the status codes
       returned by the drive.


                                

                            Table 64
                          Status Codes


       Descriptions of the status codes are given below:

       GOOD -  This status  byte  indicates  that  the  operation
       completed as expected.

       CHECK  CONDITION  -  Any  error,  exception,  or  abnormal
       condition that  causes sense data to be set causes a CHECK
       CONDITION status.   The  REQUEST SENSE  command should  be
       issued following  a CHECK  CONDITION status,  to determine
       the condition.

       NOTE: If any  command other  than REQUEST SENSE or INQUIRY
       is issued  following a  CHECK CONDITION, the sense data is
       lost.





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       BUSY - The drive returns this status whenever it is unable
       to accept  a command.   The drive returns this status when
       it is  busy doing  self-tests and self configuration after
       being powered  up or  reset, or  if it is busy executing a
       previously received command.

       INTERMEDIATE/GOOD -  This status  is  returned  for  every
       command in  a series  of linked  commands (except the last
       command),  unless   an  error,   exception,  or   abnormal
       condition causes a CHECK CONDITION status or a RESERVATION
       CONFLICT status  to be  set.    If  the  INTERMEDIATE/GOOD
       status is  not returned,  the chain  of linked commands is
       broken; no further commands in the series are executed.

       RESERVATION CONFLICT - This status is returned whenever an
       initiator attempts  to access  a drive that is reserved by
       another initiator.


6.5.6     MESSAGE Phase

       The MESSAGE  phase is  used to  transfer information about
       exception conditions  between the initiator and the drive.
       The MESSAGE IN and MESSAGE OUT phases are discussed below,
       followed by  descriptions of  the SCSI  messages.  Message
       codes supported  by the  drive are  shown  in  Table  65,
       Message Codes.


                                

                            Table 65
                          Message Codes



A    MESSAGE IN PHASE

       During the MESSAGE IN phase, a message is transferred from
       the drive  to the  initiator.   The drive  may enter  this
       phase at any time.


B    MESSAGE OUT PHASE

       During the  MESSAGE OUT  phase, a  message is  transferred
       from the  initiator to  the drive.  The initiator requests
       that the  drive enter  the MESSAGE  OUT phase by asserting
       the -ATN  line.   The drive  frequently monitors  the -ATN
       line and  enters the  MESSAGE OUT  phase at  its  earliest
       convenience in  response to the initiator's assertion of -
       ATN.





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       After  being  selected,  the  drive  checks  if  -ATN  was
       inserted with  the selection.   If  the initiator has -ATN
       asserted, the  drive requests a message from the initiator
       by asserting -REQ.  The first message is expected to be an
       IDENTIFY message.   If  any other message is received, the
       drive goes  to the  BUS FREE  phase with a CHECK CONDITION
       status  and  the  sense  key/error  code  set  to  ABORTED
       COMMAND/Inappropriate/Illegal Message  (0Bh/49h).  Section
       6.6, SYNCHRONOUS  DATA TRANSFER  REQUEST Message, provides
       additional information.

       If, during  the selection,  the initiator  does not assert
       its ID  on the  bus, or  -ATN is  not asserted,  the drive
       assumes the initiator cannot support DISCONNECT/RECONNECT.

       NOTE: If   the    initiator   expects    the   drive    to
       disconnect/reconnect, then  a MESSAGE  OUT phase (IDENTIFY
       with bit  six true)  must occur  immediately  following  a
       SELECTION phase  which had  both the  initiator's and  the
       drive's SCSI device ID asserted on the bus.


C    COMMAND COMPLETE (00h)

       This message  is sent  from the  drive to the initiator to
       indicate that  the execution  of a command (or a series of
       linked commands) has terminated, and that valid status has
       been sent  to the  initiator.   After sending this message
       successfully, the  drive goes  to the  BUS FREE  phase  by
       releasing -BSY unless the initiator sets the -ATN line.

       NOTE: The command  may  or  may  not  have  been  executed
       successfully, as indicated in the status.

       If the  initiator rejects  this  message  with  a  MESSAGE
       REJECT, the  drive goes to the BUS FREE phase and does not
       consider this an error.


D    SAVE DATA POINTER (02h)

       When doing  disconnects, this message is sent before every
       DISCONNECT message.  If the initiator rejects this message
       with a MESSAGE REJECT, the drive does not disconnect.


E    RESTORE POINTERS (03h)

       This message is sent from the drive to the initiator.  The
       message acts  to restore  to the  active  state  the  most
       recently saved pointers for the currently attached logical
       unit.  Pointers to the command, data, and status locations
       for the  logical unit are restored to the active pointers.
       Command and  status pointers are restored to the beginning



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       of the present command and status areas.  The data pointer
       is restored  to the  value at  the beginning  of the  data
       area, or  to the value at the point at which the last SAVE
       DATA POINTERS message occurred for that logical unit.

       If the  initiator rejects  this  message  with  a  MESSAGE
       REJECT,  the  drive  immediately  terminates  the  present
       command with  a CHECK  CONDITION status and sets the sense
       key/error code  to ABORTED  COMMAND/Message  Reject  Error
       (0Bh, 43h) for that initiator.

       When the  drive  reselects  the  initiator,  the  IDENTIFY
       message implies  that the  initiator  should  restore  its
       pointers.  Therefore, this message is not normally used in
       reselection.


F    DISCONNECT (04h)

       This  message  is  sent  from  the  drive  to  inform  the
       initiator that  the present  physical path  is about to be
       broken (the  drive plans to disconnect by releasing -BSY),
       but that  a  later  reconnect  is  required  in  order  to
       complete the  current operation.   This  message does  not
       cause the  initiator to  save the  data pointer.   If  the
       initiator rejects  this message with a MESSAGE REJECT, the
       drive does not disconnect.


G    INITIATOR DETECTED ERROR (05h)

       This message is issued by an initiator to inform the drive
       that an  error has  occurred during  an operation.    This
       message should  be sent  by the  initiator when  a  parity
       error is  detected.   The disk  drive aborts  the  current
       command  with   a  CHECK  CONDITION  status  and  a  sense
       key/error code  of ABORTED  COMMAND/Initiator Detect Error
       (0Bh/48h).


H    ABORT (06h)

       This message  is sent  from the  initiator to the drive to
       clear the  present operation.  All pending data and status
       for the  issuing initiator  is cleared from the drive, and
       the drive  goes to  the BUS  FREE phase.  Pending data and
       status for  other initiators is not cleared.  No status or
       ending message  is sent  for the  operation.  It is not an
       error to  issue this message to a logical unit that is not
       currently performing an operation for the initiator.







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I    MESSAGE REJECT (07h)

       This message  is sent  from either  the initiator  or  the
       drive to  indicate that  the  last  message  received  was
       inappropriate or has not been implemented.

       In order  to  indicate  its  intentions  in  sending  this
       message, the  initiator asserts  -ATN prior to its release
       of -ACK  for the  handshake of the message to be rejected.
       When the  drive sends  this message, it changes to MESSAGE
       IN phase  and  sends  this  message  prior  to  requesting
       additional  message   bytes  from  the  initiator.    This
       provides an  interlock so that the initiator can determine
       which message is rejected.

       If the  initiator responds  to this message with a MESSAGE
       REJECT  message,  the  drive  immediately  terminates  the
       present command with a CHECK CONDITION status and sets the
       sense key/error  code to  ABORTED  COMMAND/Message  Reject
       Error (0Bh, 43h) for that initiator.


J    NO OPERATION (08h)

       The initiator  sends this  message when  it has  no  valid
       message for  the drive  request.   The drive  receives and
       ignores this message.


K    MESSAGE PARITY ERROR (09h)

       The initiator  sends this  message to  indicate  a  parity
       error on  one or  more bytes of the last message sent from
       the drive.   The initiator asserts -ATN prior to releasing
       -ACK for  the last  byte of  the message in error, so that
       the drive knows which message is in error.  The drive goes
       to the  BUS FREE  phase and aborts the current command for
       that initiator.  No further reconnection is attempted, and
       neither STATUS  nor COMMAND COMPLETE messages are returned
       for the  command.   The sense  key/error code  is  set  to
       ABORTED  COMMAND/Parity   Error  (0Bh,   47h)   for   that
       initiator.


L    LINKED COMMAND COMPLETE (0Ah)

       This message is sent to the initiator to indicate that the
       execution of a linked command has completed and the status
       has been sent.

       If the  initiator responds  with a MESSAGE REJECT message,
       the drive  goes to the BUS FREE phase and does not execute
       the next  command in  the chain.  The sense key/error code




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       is set  to ABORTED COMMAND/Message Reject Error (0Bh, 43h)
       for that initiator.


M    LINKED COMMAND COMPLETE (WITH FLAG) (0Bh)

       This message is sent to the initiator to indicate that the
       execution of  a linked  command (with  the flag bit set to
       one) has completed and that the status has been sent.

       If the  initiator responds  with a MESSAGE REJECT message,
       the drive  goes to the BUS FREE phase and does not execute
       the next  command in  the chain.  The sense key/error code
       is set to ABORTED COMMAND/Message Reject Error (0Bh, 43h).


N    BUS DEVICE RESET (0Ch)

       An initiator  may send  this message to the drive to clear
       all current  commands on  that SCSI  device.    The  drive
       clears all  commands, goes  through its  initial power  up
       checks, its  self configuration,  and goes to the BUS FREE
       state ("hard" RESET).


O    IDENTIFY (C0h/80h)

       This message  is sent  by an  initiator after it selects a
       drive.  It is sent by the drive as the first message after
       a reconnect.  In addition, this message specifies that the
       sender supports some or all of the optional messages.  The
       bits in  Table 66,  IDENTIFY Message Codes, show that the
       only truly  changeable bit  is  bit  six;  therefore,  the
       command   can    have   only   two   values:      C0h   if
       disconnect/reconnect     is      supported,     80h     if
       disconnect/reconnect is not supported.


                                

                            Table 66
                     IDENTIFY Message Codes


       If the  initiator responds  to this message with a MESSAGE
       REJECT, the  drive goes to the BUS FREE phase and sets the
       sense key/error  code to  ABORTED  COMMAND/Message  Reject
       Error (0Bh, 43h) for that initiator.

       NOTE: The  drive   does  not  disconnect  if,  during  the
       SELECTION phase,  the initiator does not set its initiator
       SCSI device  ID on  the bus, and if the initiator does not





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       send an  IDENTIFY message  out (with  bit six  set) to the
       drive.


6.6  SYNCHRONOUS DATA TRANSFER REQUEST MESSAGE (01h)

       Presently the  Synchronous Data Transfer option is not yet
       supported and will be determined at a later date.

       The  drive   can,  optionally,  perform  synchronous  data
       transfers, as discussed in section 6.5.2, Synchronous Data
       Transfer.   A pair  of SYNCHRONOUS  DATA TRANSFER  REQUEST
       messages (see Table 67, SYNCHRONOUS DATA TRANSFER REQUEST
       Byte Values)  are exchanged  between an  initiator and the
       drive under the following conditions:

         A SCSI  device that  supports synchronous data transfer
         recognizes it  has not  communicated with the other SCSI
         device since receiving the last "hard" RESET.

         A SCSI  device that  supports synchronous data transfer
         recognizes it  has not  communicated with the other SCSI
         device since receiving a BUS DEVICE RESET message.

       SCSI devices  may  also  exchange  messages  to  establish
       synchronous data  transfer when  requested to  do so.  The
       messages exchanged  establish the  transfer period and the
       -REQ/-ACK offset.


                                

                            Table 67
          SYNCHRONOUS DATA TRANSFER REQUEST Byte Values


       The transfer period is defined as the minimum time between
       the leading  edge of a -REQ pulse and of its corresponding
       -ACK pulse.   The  -REQ/-ACK  offset  is  defined  as  the
       maximum number  of -REQ  pulses that  may  be  outstanding
       before the  corresponding -ACK  pulse is  received at  the
       drive.   A -REQ/-ACK  offset value of zero indicates asyn-
       chronous mode; a value of 0Fh yields the maximum number of
       outstanding -REQ pulses supported (15).

       If the  initiator recognizes that negotiation is required,
       it asserts  -ATN and,  if  the  drive  implements  message
       transfers,  sends  a  SYNCHRONOUS  DATA  TRANSFER  REQUEST
       message,  specifying  the  -REQ/-ACK  offset  and  minimum
       transfer period.   The  -REQ/-ACK offset is chosen to meet
       the data  handling requirements  of the  target, while the
       minimum  transfer  period  is  chosen  to  meet  the  data





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       handling  requirements   of  the  initiator.    The  drive
       responds in any of the following ways:

       Drive Response               Implied Agreement
       


       -REQ/-ACK offset  less than or                                    -REQ/-ACK  offset   equal  to
       equal to the requested value.                                    drive value.

       Minimum transfer  period equal                                    Minimum transfer period equal
       to or  greater than  requested                                    to the drive value.
       period.

       -REQ/-ACK  offset   equal   to                                    Asynchronous transfer.
       zero.

       MESSAGE REJECT.              Asynchronous transfer.

       The implied agreement remains in effect until a BUS DEVICE
       RESET  message  is  received,  a  "hard"  RESET  condition
       occurs, or  until one  of the  two SCSI  devices elects to
       modify the agreement.  Renegotiation at every selection is
       not recommended  since a significant performance impact is
       likely.   The default  mode  of  data  transfer  is  asyn-
       chronous.   The default mode is entered at power on, after
       a BUS  DEVICE RESET  message,  or  after  a  "hard"  RESET
       condition.   The SYNCHRONOUS DATA TRANSFER REQUEST message
       exchange can  only take  place following a SELECTION phase
       that includes  the SCSI IDs for both the initiator and the
       target.   Violation of  this rule  may make  data transfer
       impossible owing to disagreements among SCSI devices about
       the data transfer mode.


6.7  ERROR CONDITIONS

       Under several  error conditions,  the  drive  changes  the
       phase  to  BUS  FREE  without  correctly  terminating  the
       command  (that  is,  no  DISCONNECT  or  COMMAND  COMPLETE
       message is  sent).    The  drive  clears  all  information
       regarding the  command, except  sense data  (if any),  and
       does not  attempt  to  reconnect,  or  in  any  other  way
       terminate, the command.  The initiator must assume this is
       a catastrophic  failure and return the error to the system
       software.

       Sense data  may or  may not  be valid  when this condition
       occurs.   If the  initiator issues a REQUEST SENSE command
       and the  returned sense  key/error code  is anything other
       than 00h/00h, the sense data is valid.






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6.7.1     MESSAGE OUT Phase Parity Error

       If the drive detects a parity error during the MESSAGE OUT
       phase, the  drive processes  the error using the following
       sequence:

         The drive  terminates the  present command with a CHECK
          CONDITION status  and sets  the sense key/error code to
          ABORTED COMMAND/Parity  Error (0Bh/47h).    This  error
          does not  prevent the initiator from trying the command
          again.


6.7.2     COMMAND Phase Parity Error

       When the  drive detects  a parity error during the COMMAND
       phase, the  drive aborts  the command  using the following
       sequence:

         The disk  drive terminates  the command  with  a  CHECK
          CONDITION status  and sets  the sense key/error code to
          ABORTED COMMAND/Parity  Error (0Bh/47h).    This  error
          does not  prevent the initiator from trying the command
          again.


6.7.3     DATA OUT Phase Parity Error

       If the  drive detects  a parity  error during the DATA OUT
       phase, it  terminates the  command with  a CHECK CONDITION
       status, and  sets the  sense  key/error  code  to  ABORTED
       COMMAND/Parity Error  (0Bh/47h).    This  error  does  not
       prevent the initiator from trying the command again.


6.7.4     Initiator Detected Error

       If the  drive receives an initiator detected error message
       at any  time during  the command, except during the STATUS
       phase or  COMMAND  COMPLETE  message,  it  terminates  the
       current command with a CHECK CONDITION status and sets the
       sense key/error code to ABORTED COMMAND/Initiator Detected
       Error  (0Bh/48h).     This  error  does  not  prevent  the
       initiator from trying the command again.

       If the initiator sends an initiator detected error message
       immediately after  the STATUS phase, the drive immediately
       goes to  the BUS  FREE phase.  The sense key/error code is
       set to ABORTED COMMAND/Initiator Detected Error (0Bh/48h).
       This error  does not prevent the initiator from trying the
       command again.

       If the initiator sends an initiator detected error message
       immediately after  the COMMAND  COMPLETE message  is sent,



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       the drive  immediately goes  to the  BUS FREE  phase.  The
       sense key/error  code is  set to ABORTED COMMAND/Initiator
       Detected Error (0Bh/48h).  This error does not prevent the
       initiator from trying the command again.


6.7.5     REJECTED Message

       When the  drive receives a MESSAGE REJECT message from the
       initiator, the  drive takes  one of the following actions,
       based on which message was rejected:

         COMMAND COMPLETE - The drive goes to the BUS FREE phase
          and does not consider this an error.

         DISCONNECT -  The drive  does not  disconnect from  the
          initiator and  continues the  current  command.    This
          condition does  not preclude  the drive from attempting
          to disconnect at a later time.

          NOTE:     The drive  does not send a DISCONNECT message
          to  an   initiator   which   does   not   support   the
          disconnect/reconnect option.

         IDENTIFY (Reconnect)  - The  drive immediately  goes to
          the BUS FREE phase and aborts the current SCSI command.
          No further  reconnection is attempted, and no STATUS or
          COMMAND COMPLETE  message is sent for the command.  The
          sense key/error  code is set to ABORTED COMMAND/Message
          Reject Error (0Bh, 43h).

         LINKED COMMAND COMPLETE - The drive immediately goes to
          the BUS  FREE phase  and does not read the next command
          in the linked list.  The sense key/error code is set to
          ABORTED COMMAND/Message Reject Error (0Bh, 43h).

         MESSAGE REJECT  - The  drive immediately terminates the
          present command  with a CHECK CONDITION status and sets
          the sense  key/error code  to  ABORTED  COMMAND/Message
          Reject Error (0Bh, 43h).

         RESTORE POINTERS  - Since  the RESTORE POINTERS message
          is only  used in  an error recovery or retry situation,
          the drive aborts the recovery or retry attempt, assumes
          the error  is unrecoverable,  and completes the command
          according to the error condition.

         SAVE DATA  POINTER -  The drive  assumes the  initiator
          does not  support this  message and does not attempt to
          disconnect from the bus during this command.







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6.7.6     Initiator MESSAGE PARITY ERROR

       When the  drive receives  a MESSAGE  PARITY ERROR  message
       from the  initiator, the drive immediately goes to the BUS
       FREE phase,  and aborts  the current  SCSI  command.    No
       further  reconnection  is  attempted,  and  no  STATUS  or
       COMMAND COMPLETE message is returned for the command.  The
       sense key/error  code is  set  to  ABORTED  COMMAND/Parity
       Error (0Bh/47h).


6.7.7     RESELECTION Time-Out

       When the  drive attempts to reselect the initiator and the
       initiator does  not respond  within a  selection  time-out
       delay (as  defined in  the SCSI standard), the reselection
       is aborted.   No further reconnection is attempted, and no
       STATUS or  COMMAND COMPLETE  message is  returned for  the
       command.   The sense  key/error code  is  set  to  ABORTED
       COMMAND/Select-Reselect Time-Out (0Bh/45h).

       NOTE: The initiator must have an overall  command time-out
       delay to detect this error.


6.7.8     Internal Controller Errors

       If an  error occurs within the embedded controller that is
       related to  the  SCSI  hardware  or  firmware,  the  drive
       terminates the  present command  with  a  CHECK  CONDITION
       status and  sets the  sense  key/error  code  to  HARDWARE
       ERROR/SCSI Hardware  Error (04h/).   This  error does  not
       prevent the initiator from trying the command again.
























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7.0  SCSI COMMAND DESCRIPTIONS

       This chapter describes the SCSI commands implemented by
       the  Maxtor   LXT-200S  disk   drives.     The  command
       descriptions are  listed alphabetically  as a reference
       aid.   The SCSI Command Overview explains the fields in
       the command  descriptor block  (CDB) that are common to
       all commands.    Each  individual  command  description
       explains the  command function,  the CDB,  and any data
       returned.


7.1  SCSI COMMAND OVERVIEW

       This section  describes the fields in the CDB common to
       every command.   Each  SCSI command  is described  in a
       separate subsection, including CDB formats, hexadecimal
       operation  code,   byte  and  bit  functions,  and  any
       necessary effects produced by the commands.

       A request  from the initiator is performed by sending a
       CDB to  the drive.   For  some commands, the request is
       accompanied  by   a  list   of  parameters,   or  other
       information sent  during the  DATA OUT phase, or a list
       may be  returned to the initiator from the drive during
       the DATA  IN phase.   Table 71, Typical CDB for 6-Byte
       Commands,  and  Table  72,  Typical  CDB  for  10-Byte
       Commands,  show   the  basic   organization  of   CDBs.
       Explanations of those fields which are common among all
       commands follow.


                               

                          Table 71
               Typical CDB for 6-Byte Commands



                               

                          Table 72
               Typical CDB for 10-Byte Commands


       The reserved  bits, bytes,  fields, and code values are
       set aside  for future  standardization.   Reserved bits
       are not  checked by  the drive,  but should  be set  to
       zero.

       The operation  code is  the first byte, byte zero, of a
       CDB.   See Table  73, CDB  Operation Code Format.  The





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       operation code  contains two fields:  the group code in
       the high-order three bits, bits five through seven, and
       the command  code in the low-order five bits, bits zero
       through four.   The  group code specifies the length of
       the CDB and, together with the command code, determines
       the operation to be performed.  If the specified opera-
       tion code  is invalid  or not  implemented,  the  drive
       returns  a  CHECK  CONDITION  status  with  an  ILLEGAL
       REQUEST/Invalid Command (05h/20h) sense key/error code.


                               

                          Table 73
                  CDB Operation Code Format


       The group code specifies one of the following groups:

          Group 0   - 6-byte commands (see Table 71).
          Group 1 & 7    - 10-byte commands (see Table 72).

       The command code specifies one of the commands in Table
       74, CDB Operation Codes.


                               

                          Table 74
                     CDB Operation Codes


       The logical unit number (LUN) field contains the number
       of the  device being addressed.  The drive, acting as a
       SCSI bus  target, supports  only an  LUN field value of
       zero.   Therefore, the value for the LUN field (in byte
       one of  the CDB)  is limited  to 000  (binary).   If an
       invalid LUN field value is specified, the drive returns
       a   CHECK    CONDITION   status,    with   an   ILLEGAL
       REQUEST/Invalid LUN  (05h/25h)  sense  key/error  code.
       The drive provides this method of addressing the device
       for initiators  that  do  not  implement  the  IDENTIFY
       message.   An LUN  specified in  the  IDENTIFY  message
       overrides any LUN specified in the CDB.

       The relative  address (RelAdr)  bit  is  not  currently
       supported.   When it  is implemented  it will be set to
       one to  indicate that  the LBA  portion of the CDB is a
       twos  complement   displacement.     This  negative  or
       positive displacement is added to the LBA last accessed
       on the  logical unit, to form the LBA for this command.






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       This  feature  will  only  be  available  when  linking
       commands, and  it requires  that a  previous command in
       the linked  group has  accessed a  block of data on the
       logical unit.

       The LBA  field begins with block zero and is contiguous
       up to  the last  logical block.   The  maximum  LBA  is
       variable, depending  on the parameters selected for the
       number of  bytes per  sector and  number  of  alternate
       sectors.

       NOTE: The maximum  LBA allowable  is returned to a READ
       CAPACITY command  with a  partial media indicator (PMI)
       bit equal to zero.

       Group 0 commands contain 21-bit LBAs.

       Group 1 and 7 commands contain 32-bit LBAs.

       The control  byte is  the last  byte in every CDB.  The
       control byte  is separated  into three fields, as shown
       in Table 75, Control Byte.


                               

                          Table 75
                         Control Byte


       Bits seven through two are reserved.

       Bit one is defined as the flag bit, and is only checked
       when the  link bit is set to one.  When the flag bit is
       zero, the drive sends a LINKED COMMAND COMPLETE message
       when the  command completes  successfully.  If the flag
       bit is  set to  one, the  drive sends  a LINKED COMMAND
       COMPLETE (WITH FLAG) message when the command completes
       successfully.

       Bit zero  is defined as the link bit.  When the current
       command completes  successfully and the link bit is set
       to one,  the  drive  returns  an  INTERMEDIATE  status,
       followed by one of the two messages defined by the flag
       bit above.   The  drive then automatically links to the
       next command.   If  a linked  command is  not completed
       successfully,  the  drive  returns  a  CHECK  CONDITION
       status, and does not link to the next command.









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       The remaining  bytes in  the CDB  are primarily command
       dependent,  and   are  described   in   the   following
       individual command sections.






















































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FORMAT UNIT - 04h
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                                             FORMAT UNIT - 04h


7.2  FORMAT UNIT - 04h

       The FORMAT  UNIT command  ensures  that  the  media  is
       formatted so that all data blocks can be accessed.  The
       drive maintains  a defective  sector and  track file on
       the disk  on a  cylinder that  is inaccessible  to  the
       initiator.     During  the   formatting  process,   the
       initiator may  specify a  set of  defective  blocks  or
       tracks to be reassigned using spare blocks or alternate
       tracks, as appropriate.

       The FORMAT  UNIT command  requires two disk revolutions
       to format  each track  and uses three different sets of
       defect information:

         Primary, or  Manufacturer's, Defect  List (P list) -
          The  primary   defect  list   is  supplied   by  the
          manufacturer, and is resident on the disk drive.

         Initiator Defect  List (D  list) -  This list is the
          defect descriptor(s)  supplied to  the drive  by the
          initiator in  the DATA  OUT  phase.    The  list  is
          supplied by  the initiator when bits four and two of
          byte one  of the  CDB are  set to one, and bytes two
          and/or three of the defect list header are not zero.
          If the  defect list  length (bytes two and three) of
          the  defect   list  header   is  null,   no   defect
          descriptor(s) (D  list) is transferred.  The defects
          identified by the initiator in the D list are mapped
          out and added to the grown list (G list).

         Grown Defect  List (G  list) -  This  list  includes
          defects identified to, or by, the drive (the D and G
          lists).   It does  not include  the P  list.   These
          defects are  classified as flaws appearing after the
          medium  has  been  formatted.    The  initiator  may
          request that  the current  G  list  be  used  during
          formatting (CDB  bit CmpLst+complete  list)  set  to
          zero, and FmtData set to one), or that the current G
          list be  erased and  a new one begun (CDB bit CmpLst
          set to  one, and  FmtData set  to one).   Entries to
          this G list include defects provided to the drive in
          D lists  during previous  FORMAT UNIT  commands, the
          drive C  list defects  detected during  the previous
          FORMAT  UNIT   command,  and   defects  appended  by
          successful  completion   of  the   REASSIGN   BLOCKS
          command.

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                                             FORMAT UNIT - 04h

7.2.1     Defect List Management

       The FORMAT  UNIT command  uses the  drive geometry, and
       format information  read from  a reserved  area on  the
       disk during  power up, to format the disk drive.  These
       parameters may  be changed  by using  the  MODE  SELECT
       command just  prior to issuing the FORMAT UNIT command.
       If the  information contained  in the  reserved area is
       invalid, or  cannot be  read, the  FORMAT UNIT  command
       uses the  default parameters,  as returned  by  a  MODE
       SENSE command.   See  section 7.5, MODE SENSE, later in
       this chapter.

       In order  for any  list of defects to be relocated, the
       drive's current  values for  the  alternates  per  zone
       field in  MODE SELECT, Page Code 3, or MODE SENSE, Page
       Code 3, must be greater than zero.

       The initiator may select how the drive handles the list
       by using  of the  bits in  the CDB  and the defect list
       header.  See Table 76, FORMAT UNIT CDB.

       The drive has the capability of mapping out bad sectors
       so that  the drive  medium appears  error free  to  the
       initiator.   In the  D list header, during the DATA OUT
       phase of  a FORMAT  UNIT command, the initiator may use
       the disable  primary (DPRY),  and format  options valid
       (FOV),  bits  to  request  whether  or  not  the  drive
       relocates the  P  list  recorded  by  Maxtor  prior  to
       shipment.   Also, the drive maintains, and maps out, an
       additional list  of flaws  (G  list)  on  the  disk  if
       requested by  the initiator  in the FORMAT UNIT CDB, by
       using the  complete list  (CmpLst) bit.  The G list, if
       it exists  and is  readable,  may  include  any  errors
       identified by  the initiator  in the D list supplied in
       the defect descriptors during the DATA OUT phase of the
       FORMAT UNIT  command.   The G list also includes errors
       previously identified  by all  REASSIGN BLOCK  commands
       that have  been issued  since the  last completion of a
       FORMAT UNIT command with the complete list (CmpLst) bit
       set to one.

       With the  MODE SELECT  command, the initiator specifies
       how many  sectors are  deallocated, either per track or
       per cylinder,  to handle  bad sectors.   See  the  zone
       definition  in   section  7.4.6,  Direct-Access  Device
       Format Parameters  Page, later in this chapter.  If the
       initiator deallocates  no spare  sectors with  the MODE
       SELECT command  (zero alternates  per zone),  then  the
       drive does  not map  out any  flaws or create any spare
       sectors (the initiator operating system must handle the
       defects).   If the initiator attempts either a REASSIGN

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FORMAT UNIT - 04h

       BLOCK ,  or FORMAT  UNIT command  which involves  block
       reassignment without  first deallocating spare sectors,
       the drive returns an error condition.

       The initiator  may disable the relocation of all defect
       lists (including  default format)  while  enabling  the
       deallocation of  spare sectors  (assuming  the  current
       value of  alternates per zone is greater than zero), by
       performing a  FORMAT UNIT  command 04,  18, 00, 00, 00,
       00, with a header DATA OUT phase of 00, E0 (or F0), 00,
       00.

       The  initiator   may  disable   deallocation  of  spare
       sectors,  and   relocation  of  all  defect  lists,  by
       performing a MODE SELECT command, which sets alternates
       per zone,  and alternates per volume, to zero, followed
       by a FORMAT UNIT command 04, 00, 00, 00, 00, 00.


7.2.2     SCSI Deviations

       There are no deviations.


7.2.3     Command Parameters

       The CDB  for the  FORMAT UNIT  command is  formatted as
       shown in Table 76, FORMAT UNIT CDB.


                               

                          Table 76
                       FORMAT UNIT CDB


       A format  data (FmtData)  bit of  one indicates  that a
       DATA OUT  phase takes  place during  command execution.
       The DATA  OUT phase  consists of the 4-byte defect list
       header and, if there is a nonzero defect list length, a
       D list.   The  header specifies  if the  drive  formats
       using the P list, if the drive stops on an error during
       format, and  the length  of the  D list,  if any.   The
       optional D  list follows the header during the DATA OUT
       phase.   The D  list consists  of one  or  more  defect
       descriptors.

       The format  of the  D list  is determined by the defect
       list format  defined by  bits zero  through two  of the
       CDB.   If bit  two of  byte one of the CDB equals zero,
       only the  4-byte defect list header is transferred from

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       the initiator during the DATA OUT phase.  In this case,
       the defect  list length  of the  header (bytes  two and
       three) must  equal zero.  If bit two of byte one of the
       CDB equals  one, then one or more defect descriptors is
       transferred in the bytes from index format.

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FORMAT UNIT - 04h

       A format  data (FmtData) bit of zero indicates that the
       DATA OUT  phase does  not occur  (no defect list header
       and  no   defect  descriptors   are  supplied   by  the
       initiator).  If MODE SELECT Page Code 3 (alternates per
       zone) does  not equal  zero, then  the P list is mapped
       out.   If alternates  per zone  equals  zero,  then  no
       defects are  mapped out  and the drive is not requested
       to handle  defects at  all.   No  spare  locations  are
       deallocated by  the  drive.    Further  REASSIGN  BLOCK
       commands are  rejected with  a CHECK  CONDITION  status
       with an error code NO SPARES AVAILABLE (32).

       A complete  list (CmpLst)  bit of  one indicates  the D
       list defined by the initiator during the DATA OUT phase
       of the  command execution is the complete list of known
       defects.

       NOTE: The format  data (FmtData)  bit must equal one if
       the complete list (CmpLst) bit equals one.

       A complete list (CmpLst) bit of zero indicates that the
       data supplied  by the  initiator during  the  DATA  OUT
       phase (header  only, or  header and  descriptors) is an
       addition to  existing defect  data already removed from
       the initiator-addressable  blocks.   The result is that
       the existing  G list  (if one  exists) is used.  At the
       initiator request, the P and/or D lists are also used.

       The defect list format is used to specify the format of
       the defect  descriptors used for a D list.  See section
       7.2.5, Initiator Defect List, later in this chapter.

       The interleave  factor  field  supports  an  interleave
       factor of one thru sixteen.

       NOTE: An interleave factor of zero or one requests that
       the target use its default interleave (1:1 sequential).


7.2.4     Format Modes

       The format  mode is  selected by  a combination  of the
       FORMAT UNIT  CDB, and  the defect list header.  Through
       control  of   the  appropriate  fields,  the  initiator
       determines whether  the drive's  internal defect  lists
       are used,  the initiator  is to supply the defect list,
       or both.   The D list is discussed in detail in section
       7.2.5, Initiator Defect List.

       If the  format data  (FmtData) bit  is set  to one, the
       drive  transfers   the  defect  list  header  from  the
       initiator to the drive during the DATA OUT phase of the

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                                             FORMAT UNIT - 04h

       FORMAT UNIT command.  The defect list header is 4 bytes
       long, followed by zero or more defect descriptors.  The
       header specifies  the total  number  of  bytes  in  the
       defect list and several parameters for the format mode.
       See Table 77, FORMAT UNIT Defect List Header.


                               

                          Table 77
                FORMAT UNIT Defect List Header


       The format  options valid  (FOV) bit,  when set to one,
       indicates the  other fields  in this byte are valid and
       may be  set to  one also.   If this bit is set to zero,
       bits one  through six must also be set to zero, and the
       drive formats the drive using the P list.

       The disable  primary  (DPRY)  bit,  when  set  to  one,
       specifies the drive is to format the disk without using
       the P  list.  If this bit is zero, the drive uses the P
       list.   This bit  is only  valid if  the format options
       valid (FOV) bit is set to one.

       The disable certification (DCRT) bit must be set to one
       for disabling  all of  the certification  options.  The
       drive does not support certification.

       The stop  format (STPF) bit, when set to one, specifies
       that  the   drive  terminates   the  command   when  it
       encounters an  unrecoverable error  while accessing any
       of the  defect lists.  When this bit is zero, the drive
       continues the  format operation  if any  of  the  above
       errors occur.   This  bit is  only valid  if the format
       options valid (FOV) bit is set to one.

       The vendor  unique (VU)  bit is  not supported  by  the
       drive and must be set to zero.

       The defect list length field specifies the total number
       of bytes  (not the  total number of defect descriptors)
       in the D list (provided by the initiator).  This length
       does not  include the  4 bytes in the header.  A defect
       list length  of  zero  indicates  that  no  D  list  is
       provided by  the initiator,  and is  not considered  an
       error by the drive.

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FORMAT UNIT - 04h

       The format  mode for  the drive  is specified  with the
       following bits:   format  data (FmtData), complete list
       (CmpLst), and  disable primary  (DPRY).   If the format
       options valid  (FOV) bit  in the  defect list header is
       zero, or  if the format data (FmtData) bit is zero, the
       drive treats  the disable  primary (DPRY)  and  disable
       certification (DCRT)  bits as  if they were set to zero
       and one,  respectively.   Table 78,  FORMAT UNIT Drive
       Format Modes,  lists the  format modes supported by the
       drive, and their corresponding states for the 4 bits.


                               

                          Table 78
                FORMAT UNIT Drive Format Modes



7.2.5     Initiator Defect List

       In order  for the  initiator to  provide a  D list, the
       format data  (FmtData) bit  must be  set to  one in the
       CDB, and  bits zero  through two of byte one in the CDB
       must be  set to one of the three valid options shown in
       Table 79,  FORMAT UNIT  D List  Formats.    Also,  the
       defect list  length, bytes  two and three of the defect
       list header,  must be  set to  the appropriate  nonzero
       value.   The two valid D list options, bytes from index
       and physical, are detailed as in Table 79.

       NOTE: The initiator  should use  the  drive's  internal
       defect maps, rather than sending a D list to the drive.
       Maxtor performs  extensive testing  of all  drives, and
       adds all  areas of defective or marginal performance to
       the defect  lists.    If  the  initiator  disables  the
       internal lists  using the  disable primary  (DPRY) bit,
       marginal sectors  might  cause  future  loss  of  data.
       Also,  the   drive  uses  sophisticated  algorithms  to
       determine when  to deallocate  multiple sectors  for  a
       single defect.  The limitations of the bytes from index
       format of  the  READ  DEFECT  LIST  and    FORMAT  UNIT
       commands do  not allow  for reporting  the length  of a
       defect, even though this information is stored in the P
       list.   Therefore, the  drive is  better able  to judge
       when a  defect will cross sector boundaries than is the
       initiator.

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                                             FORMAT UNIT - 04h

                               

                          Table 79
                  FORMAT UNIT D List Formats



A    D LIST BYTES FROM INDEX FORMAT

       The D  list is  transferred from  the initiator  to the
       drive during  the DATA  OUT phase  of the  FORMAT  UNIT
       command.   The D  list begins  with  a  4-byte  header,
       followed by  zero or  more 8-byte  defect  descriptors.
       When the  D list is specified using the number of bytes
       from index,  the drive  uses the  format  described  in
       Table 710,  FORMAT UNIT  Defect  Descriptor(s),  Bytes
       from Index Format.


                               

                          Table 710
  FORMAT UNIT Defect Descriptor(s), Bytes from Index Format


       The cylinder  number  of  defect  field  specifies  the
       physical cylinder number which contains the defect.

       The head  number of  defect field  specifies  the  head
       number which contains the defect.

       The defect  bytes from index field specifies the number
       of bytes  between the  index  and  the  defect  on  the
       specified track.

       The defect descriptors must be in ascending order.  For
       determining ascending  order, the  cylinder  number  of
       defect is  considered the  most significant part of the
       address, and  the defect bytes from index is considered
       the least significant part of the address.


B    D LIST PHYSICAL SECTOR FORMAT

       The defect  list is  transferred from  the initiator to
       the drive  during the DATA OUT phase of the FORMAT UNIT
       command.   The defect list begins with a 4-byte header,
       followed by  zero or  more 8-byte  defect  descriptors.
       When the defect list is specified using physical sector
       addresses, the  drive uses  the format  in Table  711,
       FORMAT  UNIT   Defect  Descriptor(s),  Physical  Sector
       Format.

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FORMAT UNIT - 04h

                               

                          Table 711
   FORMAT UNIT Defect Descriptor(s), Physical Sector Format


       The cylinder  number  of  defect  field  specifies  the
       physical cylinder number which contains the defect.

       The head  number of  defect field  specifies  the  head
       number which contains the defect.

       The defect  sector number  field specifies  the  sector
       number which contains the defect.

       The defect descriptors must be in ascending order.  For
       determining ascending  order, the  cylinder  number  of
       defect is  considered the  most significant part of the
       address, and the defect sector number is considered the
       least significant part of the address.


7.2.6     Error Conditions

       If the format mode is invalid, the drive terminates the
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Invalid Field  in  CDB  (05h/24h),  or  ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code, whichever is applicable.

       If the  stop format  (STPF) bit  is one,  and the drive
       encounters an  unrecoverable error reading or accessing
       a defect  list, the drive terminates the command with a
       CHECK CONDITION  status and  a MEDIUM ERROR/Defect List
       Error (03h/19h) sense key/error code.

       If the  drive has insufficient capacity to reassign all
       the defective  blocks, it terminates the command with a
       CHECK CONDITION  status and  a MEDIUM  ERROR/No  Defect
       Spare  Location  Available  (03h/32h)  sense  key/error
       code.

       If the  stop format  (STPF) bit  is zero, and the drive
       encounters an  error while  accessing a defect list, it
       continues the FORMAT UNIT command.  When the command is
       completed, and  no other  errors occur,  it  terminates
       with  a   CHECK  CONDITION   status  and   a  RECOVERED
       ERROR/Defect List Error (01h/19h) sense key/error code.

       If the  format options  valid (FOV)  bit in  the defect
       list header  is zero,  and the  disable primary (DPRY),
       disable certification  (DCRT), and  stop format (STPF),

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                                             FORMAT UNIT - 04h

       bits are  not zero,  the drive  terminates the  command
       with  a   CHECK  CONDITION   status  and   an   ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code.

       If the  stop format  (STPF) bit  is  one,  the  disable
       primary (DPRY) bit is zero, and the drive cannot locate
       the P  list, the  drive terminates  the command  with a
       CHECK CONDITION  status and  an ILLEGAL REQUEST/Primary
       Defect List Not Found (05h/1Ch) sense key/error code.

       If the  stop format  (STPF) bit  is zero,  the  disable
       primary (DPRY) bit is zero, and the drive cannot locate
       the P list, it continues the FORMAT UNIT command.  When
       the command  is completed,  and no  other errors occur,
       the drive  terminates with a CHECK CONDITION status and
       a  RECOVERABLE  ERROR/Primary  Defect  List  Not  Found
       (01h/1Ch) sense key/error code.

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INQUIRY - 12h
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                                                 INQUIRY - 12h


7.3  INQUIRY - 12h

       The INQUIRY  command provides  a  means  by  which  the
       initiator may request information regarding the drive.

       If an  INQUIRY command  is received  from an  initiator
       with a  pending UNIT  ATTENTION  condition,  the  drive
       executes the  INQUIRY command,  returns a  GOOD status,
       and does not clear the UNIT ATTENTION condition.

       When the  INQUIRY command  is sent to a nonexistent LUN
       (that is, any LUN other than zero), the drive transfers
       the INQUIRY  response data  back to  the initiator  and
       terminates the command with GOOD status.  The initiator
       must  examine  the  peripheral  device  type  field  to
       determine if it is a valid LUN.


7.3.1     SCSI Deviations

       There are no deviations.


7.3.2     Command Parameters

       The INQUIRY  CDB is  formatted as  shown in Table 712,
       INQUIRY CDB.


                               

                          Table 712
                         INQUIRY CDB


       The allocation  length field,  byte four, specifies the
       number of  bytes the  initiator has  allocated for  the
       returned INQUIRY  data.   An allocation  length of zero
       indicates that no data is transferred to the initiator,
       and this  is not  considered an error.  Any other value
       indicates  the   maximum  number   of  bytes  that  are
       transferred.   The drive  terminates the  data transfer
       when the  number of  bytes specified  in the allocation
       length field  is transferred,  or  when  all  available
       INQUIRY data is transferred, whichever is less.

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                                                 INQUIRY - 12h

7.3.3     Data Format

       The INQUIRY  command returns  36 bytes  of data  to the
       initiator.   This data  is formatted  as in Table 713,
       INQUIRY Response Data.


                               

                          Table 713
                    INQUIRY Response Data


       If the  LUN field  in the  CDB is  zero, the peripheral
       device type  field, byte zero, is zero to indicate that
       this is  a direct-access  device (disk  drive).  If the
       specified LUN  is nonexistent  (that is,  any LUN other
       than zero),  this field  is set to 07Fh.  A nonexistent
       LUN is  a LUN  not supported  by the  drive.  The drive
       supports a LUN equal to zero only.

       The removable  media (RMB)  bit is  always set  to zero
       because the drive does not support removable media.

       The device  type qualifier field is always zero because
       the drive supports a direct-access device.

       The ANSI  version field  is always  01h to indicate the
       drive complies with the ANSI SCSI standard X3.131-1986.

       The response  data format  field is  always set to one,
       indicating that  the drive conforms to the SCSI CCS for
       direct-access devices.

       The additional  length  field  defines  the  number  of
       parameter bytes  which follow.  The field is always set
       to 31 (1Fh).

       The vendor  identification field  is always  set to the
       ASCII string  "MAXTOR."   The string  is left justified
       and followed  by two ASCII spaces (20h), for a total of
       eight characters.

       The product  identification field  contains the  Maxtor
       product identifier  in ASCII,  followed by  the product
       name, left  justified  and  filled  with  ASCII  spaces
       (20h).  There are 16 characters in the string; the LXT-
       200S disk  drives have  the ASCII  string "LXT-200S" in
       this field.

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INQUIRY - 12h

       The revision  level field  contains the Maxtor firmware
       revision level  in ASCII.  There are four characters in
       the string.

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                                             MODE SELECT - 15h


7.4  MODE SELECT - 15h

       The MODE  SELECT command  provides a means by which the
       initiator may  specify various parameters to the drive.
       Any changes  in the  MODE SELECT parameters take effect
       immediately  after   the  MODE   SELECT   command   has
       terminated.   The MODE  SELECT command is complementary
       to the  MODE SENSE  command, which allows the initiator
       to  request   that  the   drive  send  values  for  the
       parameters to the initiator.

       The initiator  can send  the drive  optional blocks  of
       parameters  that  are  separated  into  categories,  or
       pages.   The individual  pages specify  various options
       and features which the initiator may change.

       Pages 1,  3, and  4 of the MODE SELECT data are written
       to the  disk when  the FORMAT UNIT command is executed.
       Subsequent drive power up or reset conditions cause the
       drive to read this information from the drive.

       The initiator  sends those pages to the drive for which
       it requests  parameters to  be changed.   The initiator
       may send  pages individually, or all pages at one time,
       and the  pages do not need to be sent in any particular
       order.

       It is  recommended that, prior to issuing a MODE SELECT
       command,  the   initiator  first  issue  a  MODE  SENSE
       command, with  the page code set for all pages, and the
       page control field set for current values, to determine
       which pages  are implemented,  the  page  lengths,  and
       current values.   This  should be  followed by  another
       MODE SENSE  command, with the page control field set to
       changeable values,  to determine  which values  may  be
       altered.      The   initiator   should   analyze   this
       information, and should not issue a MODE SELECT command
       which attempts to change values in fields which are not
       implemented or not changeable.

       When a  MODE SELECT  command is issued that changes any
       parameters in  pages 3  or 4,  the drive issues a CHECK
       CONDITION status  with a  sense key/error  code of UNIT
       ATTENTION/MODE SELECT  Changed Condition  (06h/2Ah)  to
       the first  command received from all initiators, except
       the one  that issued  the MODE  SELECT command.  When a
       MODE  SELECT   command  is   issued  that  changes  any
       parameters in  page 3  or 4, a FORMAT UNIT command must
       be issued prior to the next media access command.

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       The MODE  SELECT command can affect the following types
       of drive parameters:

         Saved  Values:     The  saved  values  are  all  the
          changeable MODE SELECT parameters saved by the drive
          on  the  medium  when  it  performs  a  FORMAT  UNIT
          command.   The initiator may change the saved values
          of pages 1 and/or 2 by issuing a MODE SELECT command
          with the  save parameters (SP) bit in the CDB set to
          one.   This action  does not change the saved values
          of pages 3 and 4.

         Current Values:   The  current values  are the  MODE
          SELECT parameters  used by  the drive  during normal
          drive operation.   Any MODE SELECT command issued to
          the drive changes the current values.


7.4.1     SCSI Deviations

       Only a  single block  descriptor may  be  sent  to  the
       drive.

       The drive  ignores the  number of  blocks field  in the
       block descriptor.


7.4.2     Command Parameters

       The MODE  SELECT CDB  is formatted  as shown  in  Table
       714, MODE SELECT CDB.


                               

                          Table 714
                       MODE SELECT CDB


       The page format (PF) bit is set to one to indicate that
       the format of the data sent by the initiator, after the
       MODE SELECT  header and the block descriptors (if any),
       complies with the page format as defined in the CCS.

       The  save   parameters  (SP)  bit,  when  set  to  one,
       specifies that the drive should take the current values
       for pages 1 and/or 2, and write them to the disk as the
       saved values.   Before  the drive saves the parameters,
       it makes any changes to these pages as specified in the
       current MODE  SELECT command.   If the drive encounters
       an error  during the MODE SELECT command, it terminates
       the command  without writing the parameters to the disk

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                                             MODE SELECT - 15h

       as the  saved values.   If the save parameters (SP) bit
       is zero,  the drive updates the current values and does
       not modify the saved values.

       The parameter  list length  field specifies the length,
       in bytes,  of the  parameters that  are sent  from  the
       initiator to the drive during the DATA OUT phase of the
       MODE SELECT  command.   A parameter list length of zero
       indicates that  no  data  is  transferred  and  is  not
       considered an error by the drive.


7.4.3     Parameter List Format

       The MODE SELECT parameter list is sent by the initiator
       to the  drive during  the DATA  OUT phase.   This  list
       consists of  a parameter list header, zero or one block
       descriptors, and  zero or  more page  descriptors.  The
       entire length of the parameter list is specified in the
       MODE SELECT CDB.

       The parameter list header is 4 bytes, and specifies the
       medium type and the length of the block descriptor.

       The block descriptor consists of 8 bytes, and specifies
       the medium  density, the  number  of  blocks,  and  the
       logical block length.

       The  page   descriptors  contain   various  parameters,
       separated into pages.  These parameters specify various
       options and  features which  the initiator  may change.
       One or  more pages  may be  sent during the MODE SELECT
       command.


A    PARAMETER LIST HEADER FORMAT

       The MODE SELECT parameter list header is the first part
       of the  parameter list.   The  header is  formatted  as
       shown in Table 715, MODE SELECT Parameter List Header.


                               

                          Table 715
              MODE SELECT Parameter List Header


       The medium type field must be set to zero.

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       The block  descriptor length field specifies the length
       of the  block descriptor,  in bytes,  starting at  byte
       four of the parameter list.  The drive supports zero or
       one block  descriptors per  MODE SELECT command, so the
       only valid block descriptor lengths are 0 and 8 bytes.


B    PARAMETER LIST BLOCK DESCRIPTOR FORMAT

       The MODE  SELECT block  descriptor immediately  follows
       the parameter  list header.   The drive does not report
       an  error  if  the  block  descriptor  is  not  in  the
       parameter list  (block descriptor  length equals zero).
       The block  descriptor is  formatted as  shown in  Table
       716,  MODE  SELECT  Parameter  List  Block  Descriptor
       Format.


                               

                          Table 716
      MODE SELECT Parameter List Block Descriptor Format


       The density code field must be set to zero.

       The number  of logical  blocks field  is ignored by the
       drive.

       The logical  block length field specifies the length of
       the logical  block, in bytes.  The block length must be
       equal to  the physical sector size.  The drive supports
       logical block sizes of 180 to 4,096 bytes.


C    PAGE HEADER FORMAT

       Each of  the optional page descriptors is preceded by a
       page header.   The  page header  is 2  bytes  long  and
       identifies the  page type  length.  Each page header is
       immediately  followed   by   its   corresponding   page
       parameters.

       The page  code field  identifies the  page type.  Table
       717, MODE  SELECT Page Codes, lists the page codes and
       their corresponding page descriptions.


                               

                          Table 717
                    MODE SELECT Page Codes

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       NOTE: The disconnect/reconnect  control parameters  are
       not currently supported by the disk drive.

       The page  length field specifies the number of bytes in
       the page,  not including  the page  length byte.    The
       initiator must send the entire page to the drive.


7.4.4     Error Recovery Parameters Page

       This section  specifies the  MODE SELECT error recovery
       options supported  by the  drive.   The format  for the
       error recovery  parameters page  (page code 1) is shown
       in Table  718, MODE  SELECT Error  Recovery Parameters
       (Page Code  1).  The drive saves a single copy of these
       parameters to be used by the initiators.


                               

                          Table 718
     MODE SELECT Error Recovery Parameters (Page Code 1)


       NOTE: The drive  saves this page whenever the initiator
       issues a  FORMAT UNIT, or MODE SELECT, command with the
       save parameters (SP) bit set to one.

       The automatic  write reallocation  enabled  (AWRE)  bit
       option is not currently supported by the drive and must
       be set to zero.

       The automatic  read  reallocation  enabled  (ARRE)  bit
       option is not currently supported by the drive and must
       be set to zero.

       The transfer block (TB) bit, when set to one, specifies
       that the  drive transfers the block with the data error
       before terminating  the command.    This  bit  is  only
       applicable when  a hard  error is  encountered, or when
       the disable  transfer on  error (DTE) bit is set to one
       and a recoverable error is encountered.  If this bit is
       zero, the  drive does  not transfer  the block with the
       data error.  In both cases, the drive reports the block
       address of  the block  with the error, rather than that
       of the  preceding block,  in the  sense data.   If  the
       transfer terminates  with other than a data error (that
       is, data  not found),  the drive  does not transfer the
       block.

       The  read   continuous  (RC)  bit,  when  set  to  one,
       overrides the  enable early  correction (EEC),  disable

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       transfer on  error (DTE), post error (PER), and disable
       correction (DCR)  bits, and  disables all  retries  and
       data correction.   The  transfer block  (TB) bit is not
       applicable.   When the  read continuous (RC) bit is set
       to one, the drive transfers the entire requested length
       of data  without adding  delays that  are caused by its
       error recovery schemes.  The drive sends data which may
       be erroneous,  or fabricated,  to maintain a continuous
       flow of data and avoid delays.

       The enable early correction (EEC) bit, when set to one,
       specifies that  the drive  does not  exhaust the  retry
       count before  attempting any ECC correction.  When this
       bit is  zero, the  drive exhausts  the retry  count (as
       specified in  byte three)  before it  attempts any  ECC
       correction.   Also, the  drive attempts  to recover the
       data, using  head offset and data strobe offset, before
       attempting ECC correction.

       NOTE: This field  does not  disable retries during seek
       operations.   For any  seek or  positioning error,  the
       drive performs  a recalibrate  operation, then  retries
       the seek  operation.  If the second attempt also fails,
       the drive terminates the command.

       The post  error (PER)  bit, when  set to one, instructs
       the drive  to report  any  recoverable  errors  to  the
       initiator.   This error is either reported immediately,
       or at  the normal  completion of the command, depending
       on the  state of  the disable  transfer on  error (DTE)
       bit.   The drive may terminate the data transfer before
       all data  has been  transferred, depending on the error
       encountered and  the states of the other error recovery
       bits  in  byte  two.    When  set  to  zero,  this  bit
       suppresses   the   reporting   of   recovered   errors.
       Unrecovered errors are always reported.

       The disable  transfer on  error (DTE)  bit, when set to
       one, and  when the  post error (PER) bit is set to one,
       instructs  the   drive   to   terminate   the   command
       immediately when  a recoverable  error is  encountered,
       and create  the CHECK  CONDITION status.  The drive may
       or may  not transfer the data contained in the block in
       error, depending  on the  setting of the transfer block
       (TB) bit.   The  initiator can  only  set  the  disable
       transfer on  error (DTE)  bit to  one if it has set the
       post error  (PER) bit  to one.  If the disable transfer
       on error  (DTE) bit  is zero,  the drive  continues the
       data transfer  when a recoverable error is encountered.
       When disable  transfer on  error (DTE) equals zero, and

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       post error (PER) equals one, the sense data reports the
       last recoverable error that occurred within a transfer.

       The disable  correction (DCR)  bit, when  set  to  one,
       disables ECC  correction when reading a sector from the
       disk drive.   No  correction is  attempted,  and  if  a
       correctable ECC  error  occurs  it  is  treated  as  an
       unrecoverable error.

       The retry  count field  specifies the maximum number of
       retries to  attempt when  an error is encountered.  The
       drive supports retry counts from 0 to 255.

       The correction  span field  specifies the  largest read
       data  error,  in  bits,  on  which  correction  may  be
       attempted.   The drive  supports a correction span of 0
       to 11 bits.

       The head  offset count  field is  not supported  by the
       drive and must be set to zero.

       The data strobe offset count field  is not supported by
       the drive and must be set to zero.

       The recovery  time limit  field is not supported by the
       drive and must be set to 00h.

       Table 719, MODE SELECT Error Recovery Modes, lists the
       possible error recovery modes which may occur using the
       above parameters.   Those  combinations  which  do  not
       provide any  useful function,  that  is,  terminate  on
       errors but  do not  report them,  are marked as invalid
       mode and should not be selected by the initiator.  Data
       transfers terminate  immediately for  any unrecoverable
       error.


                               

                          Table 719
               MODE SELECT Error Recovery Modes



7.4.5     Disconnect/Reconnect Parameters Page

       This    section     specifies    the     MODE    SELECT
       disconnect/reconnect parameter  options.  These options
       are not currently supported by the disk drive.

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                          Table 720
MODE SELECT Disconnect/Reconnect Control Parameters (Page Code
                              2)


       NOTE: Page code  2  options are not currently supported
       by the disk drive.

       The buffer  full ratio  field specifies  how  full  the
       internal buffer  should be  before the drive reconnects
       to transfer  the data to the initiator.  This option is
       not currently supported by the drive and must be set to
       zero.   Future versions  of the drive will support this
       option.

       The buffer  empty ratio  field specifies  how empty the
       internal buffer  should be  before the drive reconnects
       to transfer  more data from the initiator.  This option
       is not currently supported by the drive and must be set
       to zero.   Future  versions of  the drive  will support
       this option.

       The bus  inactivity limit field specifies the length of
       time, in  100 microsecond increments, that the drive is
       allowed to  stay connected  to the SCSI bus without any
       bus activity.   The  drive supports  a range  of 1 (100
       microseconds) to 650 (65,000 microseconds).  A value of
       zero in  this field  means the drive can stay connected
       to the bus indefinitely.

       The disconnect time limit field is not supported by the
       drive and must be set to zero.

       The connect  time limit  field is  not supported by the
       drive and must be set to zero.


7.4.6     Direct-Access Device Format Parameters Page

       This section  specifies the  MODE SELECT  direct-access
       device format parameters (page code 3) supported by the
       drive.   The format  for the disk format parameter page
       is shown  in  Table  721,  MODE  SELECT  Direct-Access
       Device Format Parameters (Page Code 3).

       NOTE: The drive  saves this page whenever the initiator
       issues a FORMAT UNIT command.

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                          Table 721
MODE SELECT Direct-Access Device Format Parameters (Page Code
                              3)


       The tracks  per zone field supports one track per zone.
       This field is set to one .

       The alternate  sectors per  zone  field  specifies  the
       number of alternate sectors per zone to allocate during
       formatting.

       The alternate  tracks per zone field is not used by the
       drive and must be set to zero.

       The alternate  tracks per  volume field  specifies  the
       number  of  alternate  tracks  to  deallocate  for  bad
       sectors.  A  sector is mapped onto the alternate tracks
       by the  FORMAT UNIT  or REASSIGN  BLOCK  commands  when
       relocation occurs  in a  zone whose  alternate  sectors
       have been exhausted.  This field is not changeable.

       The sectors  per track  field specifies  the number  of
       physical  sectors   per  track.    This  field  is  not
       changeable.

       The data  bytes per physical sector field specifies the
       number  of  bytes  per  physical  sector.    The  drive
       supports sector  sizes from  180  to  4,096  bytes  per
       sector.   However, today's  async drive  only  supports
       512, 1,024, and 2,048 sector sizes.

       The interleave  field is  ignored by  the drive  and is
       always  set   to  one   (1:1  ratio)   for  best  drive
       performance.  The interleave value is set in the CDB of
       the FORMAT UNIT command.

       The track  skew field  specifies the number of physical
       sectors between the last logical block of one track and
       the first logical block on the next sequential track of
       the same  cylinder.   This field's default value is set
       to one for best drive performance.

       The cylinder  skew field  is not supported by the drive
       and must always be set to zero.

       The soft  sector format (SSEC) bit cannot be set by the
       MODE SELECT  command and  the drive ignores this field.
       See section 7.5,  MODE SENSE.

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       The hard  sector format (HSEC) bit cannot be set by the
       MODE SELECT  command and  the drive ignores this field.
       See section 7.5,  MODE SENSE.

       The removable  media (RMB) bit is not used by the drive
       and must be set to zero.

       The surface  (SURF) bit   is not supported by the drive
       and must be set to zero.

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7.4.7     Rigid Disk Drive Geometry Parameters Page

       This section specifies the MODE SELECT rigid disk drive
       geometry options  (page code 4) supported by the drive.
       The format  for the  rigid disk  drive geometry page is
       shown in  Table 722,  MODE  SELECT  Rigid  Disk  Drive
       Geometry Parameters (Page Code 4).

       NOTE: The drive  saves this page whenever the initiator
       issues a FORMAT UNIT command.


                               

                          Table 722
MODE SELECT Rigid Disk Drive Geometry Parameters (Page Code 4)


       The maximum  number of  cylinders field  specifies  the
       maximum logical number of cylinders that are accessible
       by the user.  This value already takes into account the
       reserved cylinders for the alternate tracks per volume,
       defect management,   and any other reserved tracks that
       the drive  may be  using. The  most  significant  bytes
       (MSB), bytes  two and  three, must be set to zero. This
       field is not changeable by the user.

       The maximum number of heads field is not changeable and
       must be  set to  seven for  the maximum  number of data
       heads.

       The starting  cylinder - write precompensation field is
       not supported by the drive and must be set to zero.

       The starting  cylinder - reduced write current field is
       not supported by the drive and must be set to zero.

       The drive step rate field is not supported by the drive
       and must be set to zero.

       The landing zone cylinder field is not supported by the
       drive and must be set to zero.


7.4.8     Read-Ahead Control Page

       This section  describes  the  read-ahead  control  mode
       parameters supported  by the drive.  The format for the
       read-ahead control  page is  shown in Table 723, Read-
       Ahead Control Page (Page Code 8).

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                          Table 723
      MODE SELECT Read-Ahead Control Page (Page Code 8)


       The write  cache enable (WCE) bit is non-changeable and
       is set to zero.

       The multiple  selection (MS)  bit is non-changeable and
       is set to zero.

       A read cache disable (RCD) bit of one enables the drive
       to return  data from  a READ  command from  either  the
       cache or  the media.   An  RCD bit of zero disables the
       cache and  causes any  READ command to return data from
       the media only.

       Read   retention    priority    enables/disables    the
       anticipatory prefetching  of data  into the  cache that
       has not  been requested.   A  value of (Fh) enables the
       prefetching.  A value of (1h) disables the prefetching.

       Write retention  priority is  non-changeable and is set
       to (1h).

       Disable prefetch  transfer length is set to (FFBFh) and
       is non-changeable.

       Minimum  prefetch   is  set  to  (0000h)  and  is  non-
       changeable.

       Maximum  prefetch   is  set  to  (0040h)  and  is  non-
       changeable.

       Maximum prefetch  ceiling is  set to (0040h) and is non
       changeable.


7.4.9     Error Conditions

       If any  field not used or supported by the drive is not
       set to  zero, the  drive  terminates  the  MODE  SELECT
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code.

       If the  medium type  is not  set  to  zero,  the  drive
       terminates  the   MODE  SELECT  command  with  a  CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in Parameter List (05h/26h) sense key/error code.

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       If a  block descriptor  length of  other than  zero  or
       eight is  specified,  the  drive  terminates  the  MODE
       SELECT command  with a  CHECK CONDITION  status and  an
       ILLEGAL  REQUEST/Invalid   Field  in   Parameter   List
       (05h/26h) sense key/error code.

       If the  density code  is not  set to  zero,  the  drive
       terminates  the   MODE  SELECT  command  with  a  CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in Parameter List (05h/26h) sense key/error code.

       If the  bytes per  physical sector is less than 180, or
       greater than  4,096,  the  drive  terminates  the  MODE
       SELECT command  with a  CHECK CONDITION  status and  an
       ILLEGAL  REQUEST/Invalid   Field  in   Parameter   List
       (05h/26h) sense key/error code.

       If the  track skew  parameter exceeds  33  sectors  per
       track (the  inner-most zone  sector  size),  the  drive
       terminates  the   MODE  SELECT  command  with  a  CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in Parameter List (05h/26h) sense key/error code.

       If the  tracks per  zone field  is not  set to  one the
       drive terminates  the MODE  SELECT command with a CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in Parameter List (05h/26h) sense key/error code.

       If the  alternate sectors  per zone  field value is not
       within the  supported range,  the drive  terminates the
       MODE SELECT  command with  a CHECK CONDITION status and
       an ILLEGAL  REQUEST/Invalid  Field  in  Parameter  List
       (05h/26h) sense key/error code.

       If the initiator specifies an invalid mode in the error
       recovery bits,  the drive  terminates the  MODE  SELECT
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code.

       If, in  the rigid  disk drive geometry parameters page,
       the drive  receives a  value in  the maximum  number of
       heads field  that is  greater than  the actual  maximum
       number of  heads, the  drive terminates the MODE SELECT
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code.

       If the  page length  byte in  each page header does not
       match the  page length,  as specified  in this document
       and returned  by the  MODE  SENSE  command,  the  drive
       terminates  the   MODE  SELECT  command  with  a  CHECK

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MODE SELECT - 15h

       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in Parameter List (05h/26h) sense key/error code.

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MODE SENSE - 1Ah
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                                              MODE SENSE - 1Ah


7.5  MODE SENSE - 1Ah

       The MODE  SENSE command  provides a  means by which the
       initiator  may  receive  various  parameters  from  the
       drive.   MODE SENSE  is a  complementary command to the
       MODE SELECT command.

       The drive sends blocks of parameters that are separated
       into categories,  called pages.   These  pages  specify
       various options  and features  which the  initiator may
       change.   Each page  is preceded by a page code and the
       length of  the page.   The  page length  value does not
       include bytes zero or one of the page.

       The drive  maintains the  following four different sets
       of MODE SENSE data:

         Default Values:   The  default values  are stored in
          the drive  programmable read only memory (PROM), the
          disk drive, and the drive jumpers.

         Saved Values:   The saved values are the MODE SELECT
          parameters saved by the drive on the medium when the
          drive performs a FORMAT UNIT or MODE SELECT command,
          with the  save parameters  (SP) bit (in the CDB) set
          to one.

         Current Values:   The  current values  are the  MODE
          SELECT parameters  used by  the drive  during normal
          drive operation.   Any MODE SELECT command issued to
          the drive changes the current values.

         Changeable Values:   The changeable values are those
          parameters  supported  by  the  drive  that  can  be
          changed by the MODE SELECT command.

       At initialization  time (a  POWER ON or RESET condition
       has occurred,  see Chapter  2.0, Disk Drive Setup), the
       drive  copies  the  default  values  into  the  current
       values.   After the  drive spins up, it reads the saved
       values from  the drive and copies them into the current
       values.

       When the  drive completes  a FORMAT  UNIT  command,  it
       writes all  supported pages  to the  medium.    (On  an
       unformatted drive,  the current parameters are the same
       as the  default parameters.)   The  initiator may  then
       change the  current  parameters  using  a  MODE  SELECT
       command prior  to formatting  the disk drive.  When the
       FORMAT UNIT  command completes,  the drive  writes  the

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       current values  (which may  have been changed by a MODE
       SELECT command) to the medium as the saved values.


7.5.1     SCSI Deviations

       There are no deviations.


7.5.2     Command Parameters

       The MODE SENSE CDB is formatted as shown in Table 724,
       MODE SENSE CDB.


                               

                          Table 724
                        MODE SENSE CDB


       The page control field (PCF) specifies the type of page
       values  the   drive  returns:     current,  changeable,
       default, or saved.  Table 725, MODE SENSE Page Control
       Fields, lists and describes the page control fields.


                               

                          Table 725
                MODE SENSE Page Control Fields


       The  page  code  field  specifies  the  page(s)  to  be
       returned in  the MODE  SENSE data.   Table  726,  MODE
       SENSE Page  Codes, lists  and describes the page codes.
       If a  single page  is requested (that is, the page code
       is set  to one,  two, three,  or four),  the drive only
       returns the  requested  page.    The  block  descriptor
       information is always sent with MODE SENSE data.


                               

                          Table 726
                    MODE SENSE Page Codes


       NOTE: Page code  2 is  currently not  supported by  the
       disk drive.

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                                              MODE SENSE - 1Ah

       The allocation  length field  specifies the  number  of
       bytes the  initiator has  allocated for  returned  MODE
       SENSE data.  If the drive receives a zero value in byte
       four, it  does not transfer any data and does not treat
       this condition  as an  error.    A  nonzero  allocation
       length value  indicates the  maximum number of bytes to
       be transferred.  The drive terminates the DATA IN phase
       when the  number of  bytes which  have been transferred
       reaches the  value of  the allocation  length field, or
       when all available MODE SENSE data has been transferred
       to the initiator, whichever is less.


7.5.3     Parameter List Format

       The MODE  SENSE parameter  list is sent by the drive to
       the initiator  during the  DATA IN  phase.   This  list
       consists  of   a  parameter   list  header,  one  block
       descriptor, and one to four page descriptors.

       The  parameter   list  header  is  4  bytes  long,  and
       specifies the  medium type  and the length of the block
       descriptor.

       The block descriptor is 8 bytes long, and specifies the
       medium density,  the number  of blocks,  and the  block
       length.

       The  page   descriptors  contain   various   parameters
       separated into pages.  These parameters specify various
       options and  features which  the initiator  may  change
       with the  MODE SELECT  command.   The type of page data
       returned is  specified with  the  page  code  and  page
       control field (PCF) in the CDB.

       Each defined  page is  preceded by  a header of 2 bytes
       that specifies  the page code and the page length.  The
       page code  identifies the  meaning of  the bytes  which
       follow it.   The page length field indicates the number
       of bytes  supported by  the drive  for that  page.  The
       page length  value does  not include  the page  code on
       page length  bytes.   After the  header, the  pages are
       separated  into  sub-blocks  that  contain  a  list  of
       related flags and/or values.


A    PARAMETER LIST HEADER FORMAT

       The MODE  SENSE parameter list header is the first part
       of the  parameter list.   The  header is  formatted  as
       shown in Table 727, MODE SENSE Parameter List Header.

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                          Table 727
               MODE SENSE Parameter List Header


       The sense data length field specifies the length of the
       data that  is sense, returned when a MODE SENSE command
       is issued.   This  length does  not  include  the  data
       length field  itself.   The sense  data  length  varies
       depending on which page(s) are requested.

       The medium  type field indicates the medium type on the
       drive.  The drive always returns a medium type of zero.

       The write  protect (WP)  bit is  not supported  by  the
       drive and must be set to zero.

       The block  descriptor length field specifies the length
       of the block descriptor and is set to eight.


B    PARAMETER LIST BLOCK DESCRIPTOR FORMAT

       The  MODE   SENSE  parameter   list  block   descriptor
       immediately follows  the parameter  list header.    The
       block descriptor  is formatted  as shown in Table 728,
       MODE SENSE Parameter List Block Descriptor Format.


                               

                          Table 728
      MODE SENSE Parameter List Block Descriptor Format


       The density  code field  defines  the  density  of  the
       medium on  the addressed drive.  The density code has a
       value of  zero, to indicate only the default density of
       the hard disk drive is supported.

       The number  of blocks  field specifies the total number
       of logical  blocks which  use media of the density code
       defined in  byte zero.   The  number  of  blocks  field
       always returns  zeros to  indicate that all blocks have
       the same medium type.

       The logical  block length field specifies the length of
       the logical block, in bytes.

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                                              MODE SENSE - 1Ah

C    PAGE HEADER FORMAT

       Each of  the optional page descriptors is preceded by a
       page header.   The  page header  is 2  bytes  long  and
       identifies the  page type  length.  Each page header is
       immediately  followed   by   its   corresponding   page
       parameters.

       The page  code field  identifies the  page type.  Table
       729, MODE  SENSE Page  Codes, lists the page codes and
       their corresponding page descriptions.


                               

                          Table 729
                    MODE SENSE Page Codes


       NOTE: Page code  2 is  currently not  supported by  the
       disk drive.

       The page  length field specifies the number of bytes in
       the page,  not including  the page  length byte.    The
       initiator must send the entire page to the drive.


7.5.4     Error Recovery Parameters Page

       This section specifies the format of the error recovery
       parameter page  (page code  1), as returned by the MODE
       SENSE command.    See  Table  730,  MODE  SENSE  Error
       Recovery Parameters  (Page Code  1).  A copy of each of
       these parameters  is saved  for each  initiator.    The
       values returned  are for  the initiator  which sent the
       MODE SENSE command.


                               

                          Table 730
      MODE SENSE Error Recovery Parameters (Page Code 1)


       The parameter  savable  (PS)  bit,  when  set  to  one,
       indicates the that drive saves the parameters supported
       in this  page.   When the parameter savable (PS) bit is
       zero, the drive does not save the page parameters.  The
       drive always returns a one in this field.

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MODE SENSE - 1Ah

       The automatic  write reallocation enabled (AWRE) bit is
       not supported  and the  drive always  returns a zero in
       this field.

       The automatic  read reallocation  enabled (ARRE) bit is
       not supported  and the  drive always  returns a zero in
       this field.

       The transfer block (TB) bit, when set to one, specifies
       that the  drive should transfer the block with the data
       error before terminating the command.  This bit is only
       applicable when  a hard  error is  encountered, or when
       the disable  transfer on error (DTE) bit is set to one,
       and  a  recoverable  error  is  encountered.    If  the
       transfer block  (TB) bit  is zero,  the drive  does not
       transfer the block with the data error.  In both cases,
       the drive  reports the  block address of the block with
       the error,  rather than that of the preceding block, in
       the sense  data.  If the transfer terminates with other
       than a  data error (that is, data not found), the block
       is not  transferred.   If the  initiator requested  the
       changeable values,  the transfer  block (TB) bit is set
       to one.

       The  read   continuous  (RC)  bit,  when  set  to  one,
       overrides the  enable early  correction (EEC),  disable
       transfer on  error (DTE), post error (PER), and disable
       correction (DCR)  bits, and  disables all  retries  and
       data correction.   The  transfer block  (TB) bit is not
       applicable.   When the  read continuous (RC) bit is set
       to one, the drive transfers the entire requested length
       of data  without adding  delays that  are caused by its
       error recovery schemes.  The drive sends data which may
       be erroneous,  or fabricated,  to maintain a continuous
       flow of  data and  avoid  delays.    If  the  initiator
       requested the  changeable values,  this bit  is set  to
       one.

       The enable  early correction  (EEC) bit  specifies that
       the drive  should perform  a minimum  number of retries
       before applying  any correction  algorithm.   When this
       bit is set to one, the drive does not exhaust the retry
       count before  attempting any ECC correction.  When this
       bit is set to zero, the drive exhausts the retry count,
       as specified  in byte three, before it attempts any ECC
       correction.   If the initiator requested the changeable
       values, this bit is set to one.

       NOTE: The enable  early correction  (EEC) bit  does not
       disable retries  during seek  operations.  For any seek
       or positioning  error, the  drive issues  a RECALIBRATE
       command to  the drive, then retries the seek operation.

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                                              MODE SENSE - 1Ah

       If the  second attempt also fails, the drive terminates
       the command.

       The post  error (PER)  bit, when  set to one, instructs
       the drive  to report  any  recoverable  errors  to  the
       initiator.   This error is either reported immediately,
       or at  the normal  completion of the command, depending
       on the  state of  the disable  transfer on  error (DTE)
       bit.   The error  reported to the initiator is the last
       error encountered  during the  data transfer.   If mul-
       tiple errors  occur, the  drive reports  (in the  sense
       information) the  block address  of either  1) the last
       block where  the recovered  error occurred;  or 2)  the
       block with  the first  unrecoverable  error.    If  the
       initiator requested  the changeable  values,  the  post
       error (PER) bit is set to one.

       The disable  transfer on  error (DTE)  bit, when set to
       one, and  when  the post error (PER) bit is also set to
       one, instructs  the  drive  to  terminate  the  command
       immediately when  a recoverable  error is  encountered,
       and create  the CHECK  CONDITION status.  The drive may
       or may  not transfer the data contained in the block in
       error, depending  on the  setting of the transfer block
       (TB) bit.   The  initiator can  only  set  the  disable
       transfer on  error (DTE)  bit to  one if it has set the
       post error  (PER) bit  to one.  If the disable transfer
       on error  (DTE) bit is set to zero, the drive continues
       the data  transfer when  a  recoverable  error  is  en-
       countered.   If the  initiator requested the changeable
       values, the  disable transfer on error (DTE) bit is set
       to one.

       The disable  correction (DCR)  bit, when  set  to  one,
       disables ECC  correction when reading a sector from the
       drive.     No  correction   is  attempted,   and  if  a
       correctable ECC  error  occurs,  it  is  treated  as  a
       recoverable error.   If  the  initiator  requested  the
       changeable values, this bit is set to one.

       The retry  count field  specifies the maximum number of
       retries to  attempt when  an error is encountered.  The
       drive supports  retry counts  from 0  to 255 (decimal).
       If the  initiator requested the changeable values, this
       field is set to FFh.

       The correction  span field  specifies the  largest read
       data  error,  in  bits,  on  which  correction  may  be
       attempted.   The drive  supports a correction span of 0
       to 11  (decimal).    If  the  initiator  requested  the
       changeable values, this field is set to FFh.

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MODE SENSE - 1Ah

       The head  offset count  field is  not supported and the
       drive always returns a zero in this field.

       The data  strobe offset count field is not supported by
       the drive and must be set to zero.

       The recovery  time limit field is not supported and the
       drive always returns 00h in this field.


7.5.5     Disconnect/Reconnect Parameters Page

       This   section    specifies   the    format   of    the
       disconnect/reconnect parameter  page (page  code 2), as
       returned by  the MODE  SENSE command.   See Table 731,
       MODE  SENSE   Disconnect/Reconnect  Control  Parameters
       (Page Code 2).  The drive saves a copy of each of these
       parameters for  each initiator.   This  allows any  one
       initiator  to   examine  its   own  parameters  without
       affecting the parameters of any other initiator.

       NOTE: Page code  2 is  currently not  supported by  the
       disk drive.


                               

                          Table 731
MODE SENSE Disconnect/Reconnect Control Parameters (Page Code
                              2)


       The parameter  savable  (PS)  bit,  when  set  to  one,
       indicates the that drive saves the parameters supported
       in this  page.   When the parameter savable (PS) bit is
       zero, the drive does not save the page parameters.  The
       drive always returns a one in this bit.

       The buffer  full ratio  field specifies  how  full  the
       internal buffer  should be  before the drive reconnects
       to transfer  the data to the initiator.  The drive does
       not currently  support this option and always returns a
       zero in  this field.   This option will be supported in
       future releases.

       The buffer  empty ratio  field specifies  how empty the
       internal buffer  should be  before the drive reconnects
       to transfer  more data  from the  initiator.  The drive
       does not  currently  support  this  option  and  always
       returns a  zero in  this field.   This  option will  be
       supported in future releases.

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                                              MODE SENSE - 1Ah

       The bus  inactivity limit field specifies the length of
       time, in  100 microsecond increments, that the drive is
       allowed to  stay connected  to the SCSI bus without any
       bus activity.   The  drive supports a range of 1 to 650
       (100 to  65,000 microseconds).   If  the initiator  re-
       quested the  changeable values,  this field  is set  to
       FFFFh.

       The disconnect  time limit  field is  not supported and
       the drive always returns a zero in this field.

       The connect  time limit  field is not supported and the
       drive always returns a zero in this field.


7.5.6     Direct-Access Device Format Parameters Page

       This section  specifies the format of the direct-access
       device  format   parameters  page  (page  code  3),  as
       returned by  the MODE  SENSE command.   See Table 732,
       MODE SENSE Direct-Access Device Format Parameters (Page
       Code 3).


                               

                          Table 732
 MODE SENSE Direct-Access Device Format Parameters (Page Code
                              3)


       The parameter  savable  (PS)  bit  is  always  one,  to
       indicate that  the drive saves the parameters supported
       in this page.

       The tracks  per zone  field  specifies  the  number  of
       tracks per  zone.   The drive  supports one  track  per
       zone.  If the initiator requests the changeable values,
       this field  is set to 0000h, to indicate that the field
       is not changeable.

       The alternate  sectors per  zone  field  specifies  the
       number of alternate sectors per zone to allocate during
       formatting.   The drive  supports from  zero  to  three
       alternate sectors  per track,  or one  to n sectors per
       cylinder, where  n is  the number of sectors per track,
       minus one.   If  the initiator  requests the changeable
       values, this field is set to FFFFh.

       The alternate  tracks per  zone field is not supported,
       and the drive always returns a zero in this field.

 LXT-200S Family Product Specification & OEM Technical Manual
MODE SENSE - 1Ah

       The alternate  tracks per  volume field  specifies  the
       number of alternate tracks to allocate for bad sectors.
       Bad sectors are mapped onto the alternate tracks by the
       FORMAT  UNIT   or  REASSIGN   BLOCK  commands.  If  the
       initiator requests the changeable values, this field is
       set to  0000h,  to  indicate  that  the  field  is  not
       changeable.

       The sectors  per track  field specifies  the number  of
       physical sectors  per track.  If the initiator requests
       the changeable  values, this  field is set to 0000h, to
       indicate that the field is not changeable.

       The bytes  per  physical  sector  field  specifies  the
       number  of  bytes  per  physical  sector.    The  drive
       supports sectors  sizes of  180 to 4,096 bytes.  If the
       initiator requests the changeable values, this field is
       set to FFFFh.

       The interleave value field returns the interleave value
       specified in the FORMAT UNIT command when the drive was
       formatted.   If the  initiator requests  the changeable
       values, this field is set to 0000h, to indicate that it
       is an unchangeable field.

       The track  skew field  specifies the number of physical
       sectors between the last logical block of one track and
       the first logical block of the next sequential track of
       the same  cylinder.   If  the  initiator  requests  the
       changeable values, this field is set to FFFFh.

       The cylinder  skew field is not supported by the drive.
       If the  initiator requests  the changeable values, this
       field is set to 0000h to indicate that the field is not
       changeable.

       The soft sector format (SSEC) bit is not supported, and
       is always set to zero.

       The hard  sector format  (HSEC) bit  is set  to one  to
       indicate that  the drive  uses hard  sector formatting.
       If the  initiator requested the changeable values, this
       bit is set to zero.

       The removable  media (RMB)  bit is not supported by the
       drive and is always set to zero.

       The surface  (SURF) bit is not supported, and the drive
       always returns a zero in this bit.

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                                              MODE SENSE - 1Ah

7.5.7     Rigid Disk Drive Geometry Parameters Page

       This section  specifies the  format of  the rigid  disk
       drive geometry,  page code  4, as  returned by the MODE
       SENSE command.   See  Table 733, MODE SENSE Rigid Disk
       Drive Geometry Parameters (Page Code 4).


                               

                          Table 733
MODE SENSE Rigid Disk Drive Geometry Parameters (Page Code 4)


       The parameter  savable  (PS)  bit,  when  set  to  one,
       indicates that the drive saves the parameters supported
       in this  page.   When the parameter savable (PS) bit is
       zero, the drive does not save the page parameters.  The
       drive always returns a one in this bit.

       The maximum  number of  cylinders field  specifies  the
       maximum logical number of cylinders that are accessible
       by the user.  This value already takes into account the
       reserved cylinders for the alternate tracks per volume,
       defect management,   and any other reserved tracks that
       the drive  may be  using. The  most  significant  bytes
       (MSB), bytes two and three, must be set to zero. If the
       initiator requests the changeable values, this field is
       set to  0000h,  to  indicate  that  the  field  is  not
       changeable.

       The maximum number of heads field is not changeable and
       must be  set to  seven for  the maximum  number of data
       heads. If the initiator requests the changeable values,
       this field is set to 00h, to indicate that the field is
       not changeable.

       The starting  cylinder - write precompensation field is
       not supported,  and the  drive always returns a zero in
       this field.

       The starting  cylinder - reduced write current field is
       not supported,  and the  drive always returns a zero in
       this field.

       The drive  step rate  field is  not supported,  and the
       drive always returns a zero in this field.

       The landing  zone cylinder  field is not supported, and
       the drive always returns a zero in this field.

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MODE SENSE - 1Ah

7.5.8     Read-Ahead Control Parameters Page

       This section  describes  the  read-ahead  control  mode
       parameters supported  by the drive.  The format for the
       read-ahead control  page is  shown in Table 734, Read-
       Ahead Control Parameters (Page Code 8).


                               

                          Table 734
    MODE SENSE Read-Ahead Control Parameters (Page Code 8)


       The write  cache enable (WCE) bit is non changeable and
       is set to zero.

       The multiple  selection (MS)  bit is non-changeable and
       is set to zero.

       A read cache disable (RCD) bit of one enables the drive
       to return  data from  a READ  command from  either  the
       cache or  the media.   An  RCD bit of zero disables the
       cache and  causes any  READ command to return data from
       the media only.

       Read   retention    priority    enables/disables    the
       anticipatory prefetching  of data  into the  cache that
       has not  been requested.   A  value of (Fh) enables the
       prefetching.  A value of (1h) disables the prefetching.

       Write retention  priority is  non-changeable and is set
       to (1h).

       Disable prefetch  transfer length is set to (FFBFh) and
       is non-changeable.

       Minimum  prefetch   is  set  to  (0000h)  and  is  non-
       changeable.

       Maximum  prefetch   is  set  to  (0040h)  and  is  non-
       changeable.

       Maximum prefetch  ceiling is  set to (0040h) and is non
       changeable.


7.5.9     Error Conditions

       If the page code is not valid, the drive terminates the
       MODE SENSE command with a CHECK CONDITION status and an

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                                              MODE SENSE - 1Ah

       ILLEGAL REQUEST/Invalid  Field in  CDB (05h/24h)  sense
       key/error code.

       If the  drive cannot  read the default information from
       the drive,  it terminates  the  command  with  a  CHECK
       CONDITION status  and a  NOT READY/Illegal Function for
       Device Type (02h/22h) sense key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
READ - 08h
 LXT-200S Family Product Specification & OEM Technical Manual
                                                    READ - 08h


7.6  READ - 08h

       The READ  command requests that the drive transfer data
       from the  logical unit to the initiator.  It causes the
       drive to perform an implied SEEK to the cylinder, head,
       and sector, which corresponds to the specified LBA.


7.6.1     SCSI Deviations

       There are no deviations.


7.6.2     Command Parameters

       The READ  CDB is formatted as shown in Table 735, READ
       CDB.


                               

                          Table 735
                           READ CDB


       The LBA  field specifies the logical block at which the
       read operation begins.

       The transfer  length  field  specifies  the  number  of
       contiguous logical blocks of data to be transferred.  A
       transfer length  of zero  indicates  that  256  logical
       blocks are transferred.


7.6.3     Error Conditions

       If the  LBA is  invalid, and/or  if the  LBA  plus  the
       transfer length  results in  an invalid  block address,
       the drive  terminates the  READ command  with  a  CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Illegal Block
       Address (05h/21h)  sense key/error  code.   No data  is
       transferred if this condition occurs.

 LXT-200S Family Product Specification & OEM Technical Manual
READ (EXTENDED) - 28h
 LXT-200S Family Product Specification & OEM Technical Manual
                                         READ (EXTENDED) - 28h


7.7  READ (EXTENDED) - 28h

       The READ  (EXTENDED) command  requests that  the  drive
       transfer data  from the  logical unit to the initiator.
       It causes  the drive  to perform an implied SEEK to the
       cylinder, head,  and sector,  which corresponds  to the
       specified LBA.


7.7.1     SCSI Deviations

       There are no deviations.


7.7.2     Command Parameters

       The READ  (EXTENDED) CDB is formatted as shown in Table
       736, READ (EXTENDED) CDB.


                               

                          Table 736
                     READ (EXTENDED) CDB


       The LBA  specifies the  logical block at which the read
       operation begins.

       The transfer  length  field  specifies  the  number  of
       contiguous logical blocks of data to be transferred.  A
       transfer length  of zero  indicates  that  no  data  is
       transferred, and  is not  considered an  error  by  the
       drive.


7.7.3     Error Conditions

       If the  LBA is  invalid, and/or  if the  LBA  plus  the
       transfer length  results in  an invalid  block address,
       the drive terminates the READ (EXTENDED) command with a
       CHECK CONDITION  status and  an ILLEGAL REQUEST/Illegal
       Block Address  (05h/21h) sense key/error code.  No data
       is transferred if this condition occurs.

 LXT-200S Family Product Specification & OEM Technical Manual
READ BUFFER - 3Ch
 LXT-200S Family Product Specification & OEM Technical Manual
                                             READ BUFFER - 3Ch


7.8  READ BUFFER - 3Ch

       The READ BUFFER command is used in conjunction with the
       WRITE BUFFER  command  as  a  diagnostic  function  for
       testing the drive's data buffer memory and the SCSI bus
       integrity.    There  is  no  medium  access  with  this
       command.


7.8.1     SCSI Deviations

       There are no deviations.


7.8.2     Command Parameters

       The READ  BUFFER CDB  is formatted  as shown  in  Table
       737, READ BUFFER CDB.


                               

                          Table 737
                       READ BUFFER CDB


       The allocation  length field  specifies the  number  of
       bytes the  initiator has  allocated  for  the  returned
       buffer data.   An  allocation length  of  zero  is  not
       considered an  error by  the drive, and no data is sent
       to the  initiator.   The initiator  may request  up  to
       65,535 bytes  to be  transferred, including  the 4-byte
       header.   If the  number of bytes requested exceeds the
       drive buffer  size,  the  drive  transfers  the  entire
       buffer and  terminates the  command without  an  error.
       Under this  condition, the  initiator  must  check  the
       value in  the available length field in the READ BUFFER
       header  (see   Table  738,   READ  BUFFER  Header)  to
       determine the number of bytes returned.


7.8.3     Command Usage

       It is  recommended that the initiator issue the RESERVE
       UNIT command  before it issues the READ BUFFER command,
       to ensure  that no  other initiator  sends data  to the
       drive's data  buffer. After the drive has completed the
       READ BUFFER  command, the  initiator issues  a  RELEASE
       UNIT command to release the drive.

 LXT-200S Family Product Specification & OEM Technical Manual
                                             READ BUFFER - 3Ch

       To determine  the maximum  amount of  data that  can be
       transferred with  the  READ  BUFFER  and  WRITE  BUFFER
       commands, the initiator can issue a READ BUFFER command
       with the  allocation length  set to  four.  This causes
       the drive to return only the READ BUFFER header.  Bytes
       one through  three of  the header  contain the  maximum
       buffer size.


7.8.4     Data Format

       The data  returned from  the READ BUFFER command during
       the  DATA   IN  phase  consists  of  a  4-byte  header,
       immediately followed  by the  data bytes from the drive
       data buffer.   This  header is  formatted as  shown  in
       Table 738, READ BUFFER Header.


                               

                          Table 738
                      READ BUFFER Header


       The available  length field,  bytes one  through three,
       specifies the  maximum amount  of memory that the drive
       has available  in its data buffer.  This may or may not
       be the  number of bytes actually transferred, depending
       on the allocation length specified in the CDB.


7.8.5     Error Conditions

       If the  data in  the buffer has been modified since the
       last WRITE  BUFFER command  was issued,  or if no WRITE
       BUFFER command  has been  issued since  the last  RESET
       condition, the READ BUFFER command is terminated with a
       CHECK CONDITION  status and  a MISCOMPARE/Compare Error
       (0Eh/1Dh) sense  key/error code.    If  the  allocation
       length is  set to  four or  less, the  drive  does  not
       return this error.

 LXT-200S Family Product Specification & OEM Technical Manual
READ CAPACITY - 25h
 LXT-200S Family Product Specification & OEM Technical Manual
                                           READ CAPACITY - 25h


7.9  READ CAPACITY - 25h

       The READ  CAPACITY command  is used  to  determine  the
       maximum logical  block number  which can be accessed by
       the initiator.   This  command also returns the size of
       the logical  block.  The information is returned to the
       initiator during the DATA IN phase.

       In addition, the command is used to determine whether a
       file of  a given  size will  fit  within  a  physically
       contiguous space,  by requesting  the number  of blocks
       past a  specified block  before a  substantial delay is
       encountered (that is, a cylinder boundary).


7.9.1     SCSI Deviations

       There are no deviations.


7.9.2     Command Parameters

       The READ  CAPACITY CDB  is formatted  as shown in Table
       739, READ CAPACITY CDB.


                               

                          Table 739
                      READ CAPACITY CDB


       The LBA  field is  only used  when the  partial  medium
       indicator  (PMI)  bit  is  set  to  one.    This  field
       specifies the  block address  to use when computing the
       last block before a substantial delay is encountered.

       A partial  medium indicator  (PMI) bit of one indicates
       that the  information returned  is for  the  last  full
       logical block  (from the  block specified  in  the  LBA
       field) which  can be  transferred before  a substantial
       delay is encountered (that is, a cylinder boundary).  A
       partial medium  indicator (PMI)  bit of  zero indicates
       that the  information returned  is for the last logical
       block of the drive.

 LXT-200S Family Product Specification & OEM Technical Manual
                                           READ CAPACITY - 25h

7.9.3     Data Format

       The 8  bytes of  READ CAPACITY  data  is  sent  to  the
       initiator during  the DATA IN phase and is formatted as
       shown in Table 740, READ CAPACITY Data Format.


                               

                          Table 740
                  READ CAPACITY Data Format


       The LBA  field specifies  the last logical block on the
       unit (if  the partial  medium indicator  (PMI)  bit  is
       zero),  or   the  last  full  logical  block  before  a
       substantial delay is encountered (if the partial medium
       indicator (PMI) bit is one).

       The block  length  field  specifies  the  size  of  the
       logical block, in bytes.


7.9.4     Error Conditions

       If the  partial medium  indicator (PMI) bit is one, and
       the LBA  is invalid,  the  drive  terminates  the  READ
       CAPACITY command  with a  CHECK CONDITION status and an
       ILLEGAL REQUEST/Illegal  Block Address  (05h/21h) sense
       key/error code.

       If the  partial medium  indicator (PMI) bit is zero and
       the LBA  is not  zero, the  drive terminates  the  READ
       CAPACITY command  with a  CHECK CONDITION status and an
       ILLEGAL REQUEST/Invalid  Field in  CDB (05h/24h)  sense
       key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
READ DEFECT LIST - 37h
 LXT-200S Family Product Specification & OEM Technical Manual
                                        READ DEFECT LIST - 37h


7.10 READ DEFECT LIST - 37h

       The READ  DEFECT LIST  command requests  that the drive
       transfer one  or more of the defect lists maintained by
       the drive  to the initiator.  The initiator may request
       the original P list, the G list, or both.


7.10.1    SCSI Deviations

       There are no deviations.


7.10.2    Command Parameters

       The READ DEFECT LIST CDB is formatted as shown in Table
       741, READ DEFECT LIST CDB.


                               

                          Table 741
                     READ DEFECT LIST CDB


       The P  list bit,  when set to one, specifies that the P
       list should be returned by the drive during the DATA IN
       phase.   To request  both lists, this bit may be set in
       combination with the G list bit.

       The G  list bit,  when set to one, specifies that the G
       list should be returned by the drive during the DATA IN
       phase.   To request  both lists, this bit may be set in
       combination with  the P  list bit.   A  request by  the
       initiator for  a G  list to a drive that has no entries
       in the  G list  is not considered an error; instead the
       drive returns only the P list, if also requested, or if
       only the  G list  is requested, the 4-byte header, with
       the defect list length field set to zero.

       When both  the P  and G  list bits  are set to one, the
       drive returns  both lists.  The drive sends the list in
       ascending order, and merges the lists.  When both the P
       and G list bits are set to zero, the drive returns only
       the defect list header.

       The defect  list format  field specifies  the format of
       the returned defect list.  Table 742, READ DEFECT LIST
       Defect  List   Formats,  lists  the  types  of  formats
       supported by the drive.

 LXT-200S Family Product Specification & OEM Technical Manual
                                        READ DEFECT LIST - 37h

       NOTE: The initiator  should use  the  drive's  internal
       defect maps, rather than sending a D list to the drive.
       Maxtor performs  extensive testing  of all  drives, and
       adds all  areas of defective or marginal performance to
       the defect  lists.    If  the  initiator  disables  the
       internal lists  using the  disable primary  (DPRY) bit,
       marginal sectors  might  cause  future  loss  of  data.
       Also,  the   drive  uses  sophisticated  algorithms  to
       determine when  to deallocate  multiple sectors  for  a
       single defect.  The limitations of the bytes from index
       format of  the  READ  DEFECT  LIST  and    FORMAT  UNIT
       commands do  not allow  for reporting  the length  of a
       defect, even though this information is stored in the P
       list.   Therefore, the  drive is  better able  to judge
       when a  defect will cross sector boundaries than is the
       initiator.


                               

                          Table 742
             READ DEFECT LIST Defect List Formats


       NOTE: The block  format is  not supported  by the  disk
       drive.

       The allocation  length field  specifies the  number  of
       bytes the  initiator has  allocated  for  the  returned
       defect list.   The  drive terminates  the DATA IN phase
       when  the  number  of  bytes  transferred  reaches  the
       allocation length  field value, or when the entire list
       has been transferred, whichever is less.


7.10.3    Header

       The defect  list header  (see Table  743, READ  DEFECT
       LIST Header)  is transferred  from  the  drive  to  the
       initiator during  the DATA  IN phase of the READ DEFECT
       LIST command.   The defect list header is 4 bytes long,
       followed by  zero or  more  defect  descriptors.    The
       header specifies  the format  and the  total number  of
       bytes in the returned defect list.


                               

                          Table 743
                   READ DEFECT LIST Header

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READ DEFECT LIST - 37h

       The P  list bit,  when set  to one,  indicates that the
       drive returns  the P  list during  the DATA  IN  phase.
       This bit may be set in combination with the G list bit.

       The G  list bit,  when set  to one,  indicates that the
       drive returns  the G  list during  the DATA  IN  phase.
       This bit may be set in combination with the P list bit.

       The defect  list format  field specifies  the format of
       the returned  defect list.  The drive only supports the
       BYTE from INDEX and physical sector formats.

       The defect list length field specifies the total number
       of bytes  (not the  total number of defect descriptors)
       in the defect list.  This length does not include the 4
       bytes in the header.

       The defect  descriptors are  in ascending  order.   For
       determining ascending  order, the  cylinder  number  of
       defect is  considered the  most significant part of the
       address,  and  the  defect  bytes  from  index/physical
       sector is  considered the least significant part of the
       address.


7.10.4    Bytes from Index Format

       When the  bytes from  index format  is  specified,  the
       defect list,  transferred to  the  initiator  from  the
       drive during  the DATA  IN phase, is formatted as shown
       in Table  744, READ  DEFECT LIST Defect Descriptor(s),
       Bytes from Index Format.


                               

                          Table 744
READ DEFECT LIST Defect Descriptor(s), Bytes from Index Format


       The defect list format, byte one, bits zero through two
       of the  READ DEFECT  LIST header,  is  set  to  04h  to
       indicate that the list is in bytes from index format.

       The cylinder number of defect field, bytes zero through
       two of  the defect  descriptor, specifies  the physical
       cylinder number which contains the defect.

       The head  number of  defect field,  byte three  of  the
       defect descriptor,  specifies  the  head  number  which
       contains the defect.

 LXT-200S Family Product Specification & OEM Technical Manual
                                        READ DEFECT LIST - 37h

       The defect  bytes from  index field, bytes four through
       seven of the defect descriptor, specifies the number of
       bytes between the index and the defect on the specified
       track.


7.10.5    Physical Sector Format

       When the  physical  sector  format  is  specified,  the
       defect list,  transferred to  the  initiator  from  the
       drive during  the DATA  IN phase, is formatted as shown
       In Table  745, READ  DEFECT LIST Defect Descriptor(s),
       Physical Sector Format.


                               

                          Table 745
READ DEFECT LIST Defect Descriptor(s), Physical Sector Format


       The defect  list format  field,  byte  one,  bits  zero
       through two  of the  READ DEFECT LIST header, is set to
       05h to indicate the list is in physical sector format.

       The cylinder number of defect field, bytes zero through
       two of  the defect  descriptor, specifies  the cylinder
       number which contains the defect.

       The head  number of  defect field,  byte three  of  the
       defect descriptor,  specifies  the  head  number  which
       contains the defect.

       The defect  sector number  field,  bytes  four  through
       seven of  the defect  descriptor, specifies  the sector
       number which contains the defect.


7.10.6    Error Conditions

       If the  preferred defect  list format  does not specify
       bytes  from   index,  or  physical  format,  the  drive
       terminates the  READ DEFECT  LIST command  with a CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in CDB (05h/24h) sense key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
READ LONG - E8h/3Eh
 LXT-200S Family Product Specification & OEM Technical Manual
                                           READ LONG - E8h/3Eh


7.11 READ LONG - E8h/3Eh

       The READ  LONG command  requests the drive to perform a
       read operation  of one  data block  and the 6 ECC bytes
       associated with that block. The data from the block and
       the ECC  bytes are  transferred to the initiator during
       the DATA IN phase.

       NOTE: The READ  LONG command  does not  perform any ECC
       correction when reading the disk.


7.11.1    SCSI Deviations

       The drive  recognizes either  E8h or  3Eh as  being the
       READ LONG command.  Bytes 7 and 8 of the CDB define the
       "Byte Transfer  Length."   If the data in this field is
       zero, no data is transferred.


7.11.2    Command Parameters

       The READ  LONG CDB is formatted as shown in Table 746,
       READ LONG CDB.


                               

                          Table 746
                        READ LONG CDB


       The block  address field  specifies the  block at which
       the read long operation begins.

       CAUTION:     The physical location of the READ LONG and
       WRITE LONG  block address  is always computed using the
       physical sector size instead of the logical block size.


7.11.3    Error Conditions

       If the  block address  is invalid, the drive terminates
       the READ LONG command with a CHECK CONDITION status and
       an  ILLEGAL  REQUEST/Illegal  Block  Address  (05h/21h)
       sense key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
REASSIGN BLOCK - 07h
 LXT-200S Family Product Specification & OEM Technical Manual
                                          REASSIGN BLOCK - 07h


7.12 REASSIGN BLOCK - 07h

       The REASSIGN  BLOCK command  requests  that  the  drive
       relocate a  logical block(s)  from a defective physical
       sector(s) to a physical sector(s) without defect.

       During the  DATA OUT  phase, the  initiator transfers a
       defect list  that contains  the logical  block(s) to be
       reassigned.   The drive  reassigns the  physical medium
       used for each logical block specified by the initiator.
       The data  contained in  those blocks  specified by  the
       initiator may  be altered,  but the  data in  all other
       blocks is preserved.

       Successful  completion  of  a  REASSIGN  BLOCK  command
       results in one or more new entries in the G list.


7.12.1    SCSI Deviations

       There are no deviations.


7.12.2    Command Parameters

       The REASSIGN  BLOCK CDB  is formatted as shown in Table
       747, REASSIGN BLOCK CDB.


                               

                          Table 747
                      REASSIGN BLOCK CDB



7.12.3    Defect List Format

       The REASSIGN  BLOCK parameter list consists of a 4-byte
       header (Table 748, REASSIGN BLOCK Defect List Header),
       which contains the defect list length, followed by zero
       or  more  defect  descriptors.    The  length  of  each
       descriptor is 4 bytes.  This information is transferred
       from the  initiator to  the drive  during the  DATA OUT
       phase of the REASSIGN BLOCK command.

 LXT-200S Family Product Specification & OEM Technical Manual
REASSIGN BLOCK - 07h

                               

                          Table 748
              REASSIGN BLOCK Defect List Header


       The  defect  list  length  field  specifies  the  total
       length,  in  bytes,  of  the  defect  descriptors  that
       follow.   The length  is equal to four times the number
       of defect descriptors.  A defect list length of zero is
       not considered an error by the drive.

       The defect  descriptor contains  the 4-byte  defect LBA
       (see Table  749, REASSIGN  BLOCK Defect Descriptor(s))
       that specifies  the location of the defect.  The defect
       descriptors must be in ascending order.


                               

                          Table 749
             REASSIGN BLOCK Defect Descriptor(s)



7.12.4    Error Conditions

       If the  drive has insufficient capacity to reassign all
       the defective blocks, the drive terminates the REASSIGN
       BLOCK command  with a  CHECK  CONDITION  status  and  a
       MEDIUM  ERROR/No   Defect  Spare   Location   Available
       (03h/32h) sense key/error code.

       If the  defect LBA is invalid, the drive terminates the
       REASSIGN BLOCK  command with  a CHECK  CONDITION status
       and an  ILLEGAL REQUEST/Illegal Block Address (05h/21h)
       sense key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
RECEIVE DIAGNOSTIC RESULTS - 1Ch
 LXT-200S Family Product Specification & OEM Technical Manual
                              RECEIVE DIAGNOSTIC RESULTS - 1Ch


7.13 RECEIVE DIAGNOSTIC RESULTS - 1Ch

       The RECEIVE DIAGNOSTIC RESULTS command is not currently
       supported.   When  it  is,  the  command  will  request
       analysis data be sent to the initiator after completion
       of a SEND DIAGNOSTIC command.


7.13.1    SCSI Deviations

       There are no deviations.


7.13.2    Command Parameters

       The RECEIVE  DIAGNOSTIC RESULTS  CDB  is  formatted  as
       shown in Table 750, RECEIVE DIAGNOSTIC RESULTS CDB.


                               

                          Table 750
                RECEIVE DIAGNOSTIC RESULTS CDB


       The allocation  length field  specifies the  number  of
       bytes that the initiator has allocated for the returned
       diagnostic  data.     An   allocation  length  of  zero
       indicates that  no diagnostic  data is  returned.   Any
       other value  indicates the  maximum number of bytes the
       drive transfers.  The data transfer terminates when the
       number of  bytes in  the  allocation  length  has  been
       transferred, or  when all the available diagnostic data
       has been transferred, whichever is less.

       See  section  7.20,  SEND  DIAGNOSTIC,  later  in  this
       chapter for a description of data sent to the initiator
       from the  drive during  the DATA  IN phase of a RECEIVE
       DIAGNOSTIC RESULTS command.


7.13.3    Data Format

       See section 7.20, SEND DIAGNOSTIC.


7.13.4    Error Conditions

       If  the  RECEIVE  DIAGNOSTIC  RESULTS  command  is  not
       preceded  by  a  SEND  DIAGNOSTIC  command,  the  drive

 LXT-200S Family Product Specification & OEM Technical Manual
RECEIVE DIAGNOSTIC RESULTS - 1Ch

       terminates the RECEIVE DIAGNOSTICS RESULTS command with
       a CHECK CONDITION status and an ILLEGAL REQUEST/Invalid
       Command (05h/20h) sense key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
RELEASE UNIT - 17h
 LXT-200S Family Product Specification & OEM Technical Manual
                                            RELEASE UNIT - 17h


7.14 RELEASE UNIT - 17h

       The RELEASE  UNIT command  causes the drive (previously
       reserved by  the RESERVE  UNIT command) to be released.
       Once the  RELEASE UNIT  command is  issued, other  ini-
       tiators can access the drive.

       It is  not an  error to  release a  drive which  is not
       currently reserved.

       An initiator  that  holds  a  current  reservation  may
       modify that reservation by issuing another RELEASE UNIT
       command.  The superseding RELEASE UNIT command releases
       the previous  reservation when  the new  reservation is
       granted.   The previous  reservation is not modified if
       the new  reservation cannot  be granted,  and the drive
       returns a RESERVATION CONFLICT status.


7.14.1    SCSI Deviations

       The drive does not support the extent release option.


7.14.2    Command Parameters

       The RELEASE  UNIT CDB  is formatted  as shown  in Table
       751, RELEASE UNIT CDB.


                               

                          Table 751
                       RELEASE UNIT CDB


       If the  third party  reservation (3rdPty) bit is set to
       one, the  drive is  released,  provided  the  following
       conditions are true:

         The unit  was originally  reserved using  the  third
          party option in the RESERVE UNIT command.

         The same  initiator that  issued  the  RESERVE  UNIT
          command is requesting the release of the drive.

         The initiator  specifies the same SCSI bus device ID
          in the third party ID field as was specified in that
          field by the initiator in the RESERVE UNIT command.

 LXT-200S Family Product Specification & OEM Technical Manual
RELEASE UNIT - 17h

       The third  party device ID field specifies the SCSI bus
       device ID for which the drive was reserved.


7.14.3    Error Conditions

       If the  extent reservation  option  is  specified,  the
       drive terminates  the command  with a  CHECK  CONDITION
       status and  an ILLEGAL  REQUEST/Invalid  Field  in  CDB
       (05h/24h) sense key/error code.

       If the third party release option is specified, and the
       unit was  not originally  reserved with the third party
       option, the  drive terminates  the command with a CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Invalid Field
       in CDB (05h/24h) sense key/error code.

       If the third party release option is specified, and the
       third party  device ID  is not  the  same  as  the  one
       specified in  the original  RESERVE UNIT  command,  the
       drive terminates  the command  with a  CHECK  CONDITION
       status and  an ILLEGAL  REQUEST/Invalid  Field  in  CDB
       (05h/24h) sense key/error code.

       If the third party release option is specified, and the
       initiator SCSI  ID is  not the  same  as  that  of  the
       initiator which originally reserved the unit, the drive
       terminates the  command  with  a  RESERVATION  CONFLICT
       status.

 LXT-200S Family Product Specification & OEM Technical Manual
REQUEST SENSE - 03h
 LXT-200S Family Product Specification & OEM Technical Manual
                                           REQUEST SENSE - 03h


7.15 REQUEST SENSE - 03h

       The REQUEST  SENSE command  provides a  means  for  the
       initiator to  obtain more  detailed  information  after
       execution of  a command.   Typically,  a REQUEST  SENSE
       command is issued if the previous command has completed
       with  a   CHECK  CONDITION   status  returned   to  the
       initiator.

       An initiator  should issue  a REQUEST  SENSE command as
       soon as  it receives a CHECK CONDITION status to obtain
       the sense  data saved by the drive.  The sense block is
       cleared after the REQUEST SENSE command has completed.

       The disk  drive does  not support the nonextended sense
       format:  only the extended format should be used.


7.15.1    SCSI Deviations

       There are no deviations.


7.15.2    Command Parameters

       The REQUEST  SENSE CDB  is formatted  as shown in Table
       752, REQUEST SENSE CDB.


                               

                          Table 752
                      REQUEST SENSE CDB


       The allocation  length field  specifies the  number  of
       bytes of data the initiator has allocated for the sense
       information.   The drive transfers sense data until the
       allocation length  is exhausted,  or until  all of  the
       sense data  has been  transferred, whichever  is  less.
       The  count   supplied  determines  the  format  of  the
       returned sense  data, as  explained  in  the  following
       section.


7.15.3    Data Format

       The format  of the  returned sense  data depends on the
       number of  bytes specified  in  the  allocation  length

 LXT-200S Family Product Specification & OEM Technical Manual
REQUEST SENSE - 03h

       field  of   the  CDB.    Two  sense  data  formats  are
       supported:

         An allocation  length of  zero results in a transfer
          of 4 bytes in the nonextended sense data format.

         An allocation  length greater than zero results in a
          transfer of  up to  the requested  number  of  sense
          bytes,  or   until  all  the  sense  data  has  been
          transferred, in the extended sense data format.


A    EXTENDED SENSE DATA FORMAT

       The extended  sense data  format is  available for  all
       commands,  and  is  returned  by  the  drive  when  the
       allocation  length   specified  in  the  REQUEST  SENSE
       command is  greater than  0 bytes.    See  Table  753,
       REQUEST SENSE Extended Sense Data Format.


                               

                          Table 753
                  REQUEST SENSE Sense Codes


       The valid bit, when set, indicates that the information
       byte field  contains valid  information related  to the
       error condition.

       The incorrect length indicator (ILI) bit, byte two, bit
       five, when  set to one, indicates the data available in
       the drive  is larger  than the  requested transfer size
       during a  READ DATA  BUFFER command.   This  bit is not
       used by  any other  command and  is always set to zero,
       except under the condition noted above.

       The sense  key field indicates status information about
       any errors  detected during  the operation.  The errors
       are listed  and defined  in Table  754, REQUEST  SENSE
       Sense Key Codes.

 LXT-200S Family Product Specification & OEM Technical Manual
                                           REQUEST SENSE - 03h

                               

                          Table 754
                REQUEST SENSE Sense Key Codes

 LXT-200S Family Product Specification & OEM Technical Manual
REQUEST SENSE - 03h

       The information  byte field is command specific, and is
       only valid  when the  valid field  bit is  set to  one.
       Refer to  the individual  command for  the  information
       returned in this field.

       The additional  sense length field specifies the number
       of bytes of additional sense data that follows.  If the
       allocation length  specified in the CDB is too small to
       transfer the  additional  sense  data,  the  additional
       sense length  field is  not  adjusted  to  reflect  the
       truncation.     The  additional   sense  data  contains
       information that  further defines  the  nature  of  the
       CHECK CONDITION  status code.    The  additional  sense
       length byte is set to ten for all commands.

       Bytes eight through eleven are reserved, and are always
       set to zero.

       The additional  sense code  field  contains  additional
       information about  the event  that occurred.   Refer to
       Table 755,  REQUEST SENSE  Sense Codes, for a complete
       listing of  these sense  codes.  When this field is set
       to zero,  the drive  does not have any additional sense
       information.

       The field replaceable unit (FRU) field is not supported
       and is always set to zero.

       The field  pointer valid  (FPV) bit,  when set  to one,
       indicates the information in the command/data (C/D) and
       bit pointer  valid (BPV)  bits, plus  the field pointer
       field is  valid.   Normally the  field pointer  is only
       valid when  an ILLEGAL  REQUEST sense  key is returned.
       In this  situation, the  field pointer  field points to
       the byte  which caused  the error.   When this field is
       set to zero, the drive does not have any information on
       an exact CDB or location in error.

       The command/data  (C/D) bit, when set to one, indicates
       the field  pointer field  is pointing  to a byte in the
       CDB.   When this  bit is  zero, it  indicates the field
       pointer field  is pointing  to a  byte in  the  command
       parameters which  were passed  to the  drive during the
       DATA OUT  phase.   This bit  is only valid if the field
       pointer valid (FPV) bit is set to one.

       The bit  pointer valid  (BPV) bit,  when  set  to  one,
       indicates the  information in  the bit pointer field is
       valid.   This bit  is only  valid if  the field pointer
       valid (FPV) bit is set to one.

 LXT-200S Family Product Specification & OEM Technical Manual
                                           REQUEST SENSE - 03h

       The bit pointer field specifies the bit position within
       the field  indicated by  the field pointer field, which
       was incorrect  when an  ILLEGAL REQUEST  sense key  was
       returned.   This field  is  only  valid  when  the  bit
       pointer valid (BPV) bit is set to one.

       The field  pointer field  specifies the  byte  position
       that is  incorrect when an ILLEGAL REQUEST sense key is
       returned.   This field  is only  valid when  the  field
       pointer valid  (FPV) bit  is set  to one.  This pointer
       points to  either the  CDB, or  the command  parameters
       passed during  the DATA  OUT phase,  depending  on  the
       value in the control/data (C/D) bit.


B    SENSE CODES

       Table  755,  REQUEST  SENSE  Sense  Codes,  lists  and
       describes the sense codes supported by the drive.

 LXT-200S Family Product Specification & OEM Technical Manual
REQUEST SENSE - 03h

                               

                          Table 755
                  REQUEST SENSE Sense Codes



                               

                     Table 755 (cont'd)
                  REQUEST SENSE Sense Codes



                               

                     Table 755 (cont'd)
                  REQUEST SENSE Sense Codes



7.15.4    Error Conditions

       If a  CHECK CONDITION  status is  received on a REQUEST
       SENSE command, any sense data returned by the target is
       invalid.

 LXT-200S Family Product Specification & OEM Technical Manual
RESERVE UNIT - 16h
 LXT-200S Family Product Specification & OEM Technical Manual
                                            RESERVE UNIT - 16h


7.16 RESERVE UNIT - 16h

       The  RESERVE  UNIT  command  is  used  to  reserve  the
       specified drive for exclusive use by the initiator or a
       designated third  party.   This reservation  remains in
       effect until  one of  the following conditions releases
       the reservation:

         a RELEASE  UNIT command  from the  same initiator is
       received by the drive.
         a BUS  DEVICE RESET message is received by the drive
       from any initiator.
         a SCSI BUS RESET occurs.

       If a  RESERVE UNIT  command, or  any other  command, is
       received for  a drive  which  is  reserved  by  another
       initiator, the  drive returns  a  RESERVATION  CONFLICT
       status.

       An initiator  that  holds  a  current  reservation  may
       modify that reservation by issuing another RESERVE UNIT
       command.  The superseding RESERVE UNIT command releases
       the previous  reservation when  the new  reservation is
       granted.   The previous  reservation is not modified if
       the new  reservation cannot  be granted,  and the drive
       returns a RESERVATION CONFLICT status.


7.16.1    SCSI Deviations

       The drive  does  not  support  the  extent  reservation
       option.

       The drive  does not  support reservation queuing.  If a
       RESERVE UNIT  command is  received for  a logical  unit
       which is  already reserved  for a  different initiator,
       the drive returns a RESERVATION CONFLICT status.


7.16.2    Command Parameters

       The RESERVE  UNIT CDB  is formatted  as shown  in Table
       756, RESERVE UNIT CDB.


                               

                          Table 756
                       RESERVE UNIT CDB

 LXT-200S Family Product Specification & OEM Technical Manual
RESERVE UNIT - 16h

       The third  party reservation  (3rdPty)  bit  allows  an
       initiator to  reserve a drive for another device on the
       SCSI bus.   If the third party reservation (3rdPty) bit
       is set  to one,  an initiator is allowed to reserve the
       specified drive  for the  SCSI bus  device specified in
       the third  party device  ID  field.    This  option  is
       intended for  use in  multiple-initiator systems.   Any
       device that  uses the third party reservation option to
       reserve must  also  use  the  third  party  reservation
       option to  release.   See section  7.14, RELEASE  UNIT,
       earlier in  this chapter, before any other commands can
       be sent.

       The third  party device ID field specifies the SCSI bus
       device ID  of the  device being  reserved.   The ID  is
       valid only  when the third party reservation bit is set
       to one.

       The extent  bit is  not supported  and must  be set  to
       zero.

       The reservation  identification field  is not supported
       and must be set to zero.

       The extent  list length field is not supported and must
       be set to zero.


7.16.3    Error Conditions

       If the  extent, reservation  identification, or  extent
       list length  fields are  not zero, the drive terminates
       the command  with  a  CHECK  CONDITION  status  and  an
       ILLEGAL REQUEST/Invalid  Field in  CDB (05h/24h)  sense
       key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
REZERO UNIT - 01h
 LXT-200S Family Product Specification & OEM Technical Manual
                                             REZERO UNIT - 01h


7.17 REZERO UNIT - 01h

       The REZERO UNIT command requests that the drive set the
       logical unit to cylinder zero.


7.17.1    SCSI Deviations

       There are no SCSI deviations.


7.17.2    Command Parameters

       The REZERO  UNIT CDB  is formatted  as shown  in  Table
       757, REZERO UNIT CDB.


                               

                          Table 757
                       REZERO UNIT CDB

 LXT-200S Family Product Specification & OEM Technical Manual
SEEK - 0Bh
 LXT-200S Family Product Specification & OEM Technical Manual
                                                    SEEK - 0Bh


7.18 SEEK - 0Bh

       The SEEK  command causes  the  drive  to  SEEK  to  the
       cylinder of  the specified  logical block location.  If
       the  logical  block  number  specifies  a  block  on  a
       defective track, the SEEK to the alternate track is not
       performed until  the drive  receives  and  processes  a
       command which accesses the medium.


7.18.1    SCSI Deviations

       There are no deviations.


7.18.2    Command Parameters

       The SEEK  CDB is formatted as shown in Table 758, SEEK
       CDB.


                               

                          Table 758
                           SEEK CDB


       The LBA field specifies the LBA in which to seek.  When
       the SEEK  command completes  without  any  errors,  the
       read/write heads  are positioned at the cylinder of the
       specified block address.


7.18.3    Error Conditions

       If the  LBA is  invalid, the  drive terminates the SEEK
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Illegal Block Address (05h/21h) sense key/error
       code.

 LXT-200S Family Product Specification & OEM Technical Manual
SEEK (EXTENDED) - 2Bh
 LXT-200S Family Product Specification & OEM Technical Manual
                                         SEEK (EXTENDED) - 2Bh


7.19 SEEK (EXTENDED) - 2Bh

       The SEEK (EXTENDED) command causes the drive to SEEK to
       the cylinder  of the  specified logical block location.
       If the  logical block  number specifies  a block  on  a
       defective track, the SEEK to the alternate track is not
       performed until  the drive  receives  and  processes  a
       command which accesses the medium.


7.19.1    SCSI Deviations

       There are no deviations.


7.19.2    Command Parameters

       The SEEK  (EXTENDED) CDB is formatted as shown in Table
       759, SEEK (EXTENDED) CDB.


                               

                          Table 759
                     SEEK (EXTENDED) CDB


       The LBA  field specifies  the block address in which to
       seek.   When the  SEEK command  completes  without  any
       errors the  drive is  positioned at the specified block
       address.


7.19.3    Error Conditions

       If the  LBA is  invalid, the  drive terminates the SEEK
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Illegal Block Address (05h/21h) sense key/error
       code.

 LXT-200S Family Product Specification & OEM Technical Manual
SEND DIAGNOSTIC - 1Dh
 LXT-200S Family Product Specification & OEM Technical Manual
                                         SEND DIAGNOSTIC - 1Dh


7.20 SEND DIAGNOSTIC - 1Dh

       The SEND  DIAGNOSTIC  command  requests  the  drive  to
       perform diagnostic  tests on  itself.   This command is
       only supported for vendor unique commands.


7.20.1    SCSI Deviations

       Only the self-test option is currently supported.


7.20.2    Command Parameters

       The SEND DIAGNOSTICS CDB is formatted as shown in Table
       760, SEND DIAGNOSTIC CDB.


                               

                          Table 760
                     SEND DIAGNOSTIC CDB


       The self-test (SlfTst) bit directs the drive to perform
       the self-test.   No  device access  occurs during  this
       test.

       The device  off-line (DevOfl)  bit is  not supported by
       the drive and must be set to zero.

       The unit  off-line (UntOfl) bit is not supported by the
       drive and must be set to zero.

       The  device   diagnostics  perform   write  and  verify
       operations on  each surface  of the diagnostic cylinder
       of the  specified drive.   The  disk drive  performs  a
       limited power  up self-test  on the  disk drive without
       disturbing the  data.  The disk drive performs tests on
       the SCSI  chip, buffer  controller chip, disk formatter
       chip, and the RAM.

       If any  sectors on  the diagnostic  cylinder cannot  be
       written  or   verified  by   using  two  different  bit
       patterns, the drive terminates the command with a CHECK
       CONDITION status  and sets  the sense key/error code to
       MEDIA ERROR/Uncorrectable  Data Error  (03h/11h).   The
       sense information  bytes  contain  the  number  of  bad
       sectors found on this cylinder.

 LXT-200S Family Product Specification & OEM Technical Manual
                                         SEND DIAGNOSTIC - 1Dh

       The parameter list length field must be set to zero.


7.20.3    Error Conditions

       If the  device off-line  (DevOfl) bit  is not zero, the
       drive terminates  the command  with a  CHECK  CONDITION
       status and  an ILLEGAL  REQUEST/Invalid  Field  in  CDB
       (05h/24h) sense key/error code.

       If the self-test (SlfTst) bit is zero and the unit off-
       line (UntOfl) bit is not zero, the drive terminates the
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Invalid Field  in CDB (05h/24h) sense key/error
       code.

       If the  self-test (SlfTst)  bit is  set to  one and the
       parameter list  length field  is not  zero,  the  drive
       terminates the  command with  a CHECK  CONDITION status
       and an  ILLEGAL REQUEST/Invalid  Field in CDB (05h/24h)
       sense key/error code.

       If the diagnostic subcommand specified in the parameter
       list is  not legal,  the drive  terminates the  command
       with  a   CHECK  CONDITION   status  and   an   ILLEGAL
       REQUEST/Invalid Field in Parameter List (05h/26h) sense
       key/error code.

 LXT-200S Family Product Specification & OEM Technical Manual
START/STOP UNIT - 1Bh
 LXT-200S Family Product Specification & OEM Technical Manual
                                         START/STOP UNIT - 1Bh


7.21 START/STOP UNIT - 1Bh

       The START/STOP  UNIT command  requests that  the  drive
       spin up or spin down.


7.21.1    SCSI Deviations

       There are no deviations.


7.21.2    Command Parameters

       The CDB for the START/STOP UNIT command is formatted as
       shown in Table 761, START/STOP UNIT CDB.


                               

                          Table 761
                     START/STOP UNIT CDB


       The immediate  (Immed) bit,  when set to one, indicates
       that status  is to be returned as soon as the operation
       is initiated.   If the immediate bit is zero, the drive
       returns the status when the operation is completed.

       The start  bit, when  set to one, requests the drive be
       made ready  for use.  A start bit of zero requests that
       the drive be spun down.


7.21.3    Error Conditions

       If a  command which  accesses the medium is sent to the
       drive  after  a  STOP  UNIT  command  (START/STOP  UNIT
       command with  start  bit  equal  to  zero),  the  drive
       terminates the  command with  a CHECK  CONDITION status
       and sets  the sense  key/error code  to NOT READY/Drive
       Not Ready (02h/04h).

 LXT-200S Family Product Specification & OEM Technical Manual
TEST UNIT READY - 00h
 LXT-200S Family Product Specification & OEM Technical Manual
                                         TEST UNIT READY - 00h


7.22 TEST UNIT READY - 00h

       The TEST  UNIT READY  command provides  a means for the
       initiator to check whether the drive is ready.


7.22.1    SCSI Deviations

       There are no deviations.


7.22.2    Command Parameters

       The CDB for the TEST UNIT READY command is formatted as
       shown in Table 762, TEST UNIT READY CDB.


                               

                          Table 762
                     TEST UNIT READY CDB



7.22.3    Error Conditions

       If the  logical unit  is not ready, the drive returns a
       CHECK CONDITION  or BUSY  status in  response  to  this
       command.   A REQUEST  SENSE command  can be  issued  to
       obtain detailed  information about the reason the drive
       is not ready (unavailable).

 LXT-200S Family Product Specification & OEM Technical Manual
VERIFY - 2Fh
 LXT-200S Family Product Specification & OEM Technical Manual
                                                  VERIFY - 2Fh


7.23 VERIFY - 2Fh

       The VERIFY  command requests  that the drive verify the
       data  written  on  the  drive.    Verification  may  be
       performed either  as a  byte-by-byte comparison,  or by
       confirming that  the data  and ECCs  correspond to each
       other.


7.23.1    SCSI Deviations

       There are no deviations.


7.23.2    Command Parameters

       The VERIFY  CDB is  formatted as  shown in  Table 763,
       VERIFY CDB.


                               

                          Table 763
                          VERIFY CDB


       The byte  check (BytChk) bit, byte one, bit one, is not
       supported by the drive and must be set to zero.

       The LBA  field specifies the logical block at which the
       verify operation begins.

       The verification  length field  specifies the number of
       contiguous logical  blocks of  data to  be verified.  A
       verification length  of zero  indicates that no data is
       verified and is not considered an error by the drive.


7.23.3    Error Conditions

       If the  LBA is invalid, the drive terminates the VERIFY
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Illegal Block Address (05h/21h) sense key/error
       code.

       If the LBA, plus the verification length, results in an
       invalid block  address, the drive terminates the VERIFY
       command with  a CHECK  CONDITION status  and an ILLEGAL
       REQUEST/Illegal Block Address (05h/21h) sense key/error
       code.

 LXT-200S Family Product Specification & OEM Technical Manual
WRITE - 0Ah
 LXT-200S Family Product Specification & OEM Technical Manual
                                                   WRITE - 0Ah


7.24 WRITE - 0Ah

       The WRITE  command requests  that the  drive write  the
       data transferred  by the  initiator to  the medium.  It
       also causes the drive to perform an implied SEEK to the
       cylinder, head,  and sector  which corresponds  to  the
       specified LBA.


7.24.1    SCSI Deviations

       There are no deviations.


7.24.2    Command Parameters

       The CDB  for the WRITE command is formatted as shown in
       Table 764, WRITE CDB.


                               

                          Table 764
                          WRITE CDB


       The LBA  field specifies the logical block at which the
       write operation begins.

       The transfer  length  field  specifies  the  number  of
       contiguous logical blocks of data to be transferred.  A
       transfer length  of zero  indicates  that  256  logical
       blocks are transferred.


7.24.3    Error Conditions

       If the  LBA is  invalid, and/or  if the  LBA, plus  the
       transfer length,  results in  an invalid block address,
       the drive  terminates the  WRITE command  with a  CHECK
       CONDITION status  and an  ILLEGAL REQUEST/Illegal Block
       Address (05h/21h)  sense key/error  code.   No data  is
       transferred if this condition occurs.

 LXT-200S Family Product Specification & OEM Technical Manual
WRITE (EXTENDED) - 2Ah
 LXT-200S Family Product Specification & OEM Technical Manual
                                        WRITE (EXTENDED) - 2Ah


7.25 WRITE (EXTENDED) - 2Ah

       The WRITE  (EXTENDED) command  requests that  the drive
       write the  data transferred  by the  initiator  to  the
       medium.  It also causes the drive to perform an implied
       SEEK  to   the  cylinder,   head,  and   sector   which
       corresponds to the specified LBA.


7.25.1    SCSI Deviations

       There are no deviations.


7.25.2    Command Parameters

       The CDB  for the  WRITE (EXTENDED) command is formatted
       as shown in Table 765, WRITE (EXTENDED) CDB.


                               

                          Table 765
                     WRITE (EXTENDED) CDB


       The LBA  field specifies the logical block at which the
       write operation begins.

       The transfer  length  field  specifies  the  number  of
       contiguous logical  blocks of data to be transferred. A
       transfer length  of zero  indicates  that  no  data  is
       transferred, and  is not  considered an  error  by  the
       drive.


7.25.3    Error Conditions

       If the LBA field is invalid, and/or if the LBA plus the
       transfer length  results in  an invalid  block address,
       the drive  terminates the WRITE (EXTENDED) command with
       a CHECK CONDITION status and an ILLEGAL REQUEST/Illegal
       Block Address  (05h/21h) sense key/error code.  No data
       is transferred if this condition occurs.

 LXT-200S Family Product Specification & OEM Technical Manual
WRITE & VERIFY - 2Eh
 LXT-200S Family Product Specification & OEM Technical Manual
                                          WRITE & VERIFY - 2Eh


7.26 WRITE AND VERIFY - 2Eh

       The WRITE  AND VERIFY  command requests  that the drive
       write the  data transferred  from the  initiator to the
       drive and  then  verify  that  the  data  is  correctly
       written.     The  drive   supports  both   the   medium
       verification against  ECC, and  byte-by-byte comparison
       options.


7.26.1    SCSI Deviations

       There are no deviations.


7.26.2    Command Parameters

       The WRITE AND VERIFY CDB is formatted as in Table 766,
       WRITE AND VERIFY CDB.


                               

                          Table 766
                     WRITE AND VERIFY CDB


       The byte  check (BytChk) bit, byte one, bit one, is not
       supported by the drive and must be set to zero.

       The LBA  field specifies the logical block at which the
       write operation begins.

       The transfer  length  field  specifies  the  number  of
       contiguous logical blocks of data that are transferred.
       A transfer  length of  zero indicates  that no  logical
       blocks  are   transferred.     This  condition  is  not
       considered an  error and no data is written.  Any other
       value indicates  the number  of logical blocks that are
       transferred.

 LXT-200S Family Product Specification & OEM Technical Manual
WRITE BUFFER - 3Bh
 LXT-200S Family Product Specification & OEM Technical Manual
                                            WRITE BUFFER - 3Bh


7.27 WRITE BUFFER - 3Bh

       The WRITE  BUFFER command  is used  in conjunction with
       the READ  BUFFER command,  as a diagnostic function for
       testing the drive's data buffer memory and the SCSI bus
       integrity. There is no medium access with this command.

       To determine  the maximum  amount of  data that  can be
       transferred with  the  READ  BUFFER  and  WRITE  BUFFER
       commands, the initiator can issue a READ BUFFER command
       with the  allocation length  field set  to four.  Bytes
       two and three returned by the drive contain the maximum
       buffer size for the specified drive.


7.27.1    SCSI Deviations

       There are no deviations.


7.27.2    Command Parameters

       The WRITE  BUFFER CDB  is formatted  as shown  in Table
       767, WRITE BUFFER CDB.


                               

                          Table 767
                       WRITE BUFFER CDB


       The byte  transfer length field specifies the number of
       bytes the drive transfers during the DATA OUT phase, to
       its internal buffer. The transfer length includes the 4
       bytes of  header information  sent  before  the  actual
       data. A  transfer length  of zero  is not considered an
       error by  the drive,  and no  data is  expected or read
       from the initiator.


7.27.3    Data Format

       The data  sent by  the initiator  during the  DATA  OUT
       phase consists of a 4-byte header, immediately followed
       by the  data bytes  to be  written to  the  drive  data
       buffer. This  data is  formatted as  shown Table  768,
       WRITE BUFFER Data Format.

 LXT-200S Family Product Specification & OEM Technical Manual
                                            WRITE BUFFER - 3Bh

                               

                          Table 768
                   WRITE BUFFER Data Format


       The data  byte field contains the data to be written to
       the drive data buffer.


7.27.4    Error Conditions

       If the  byte transfer  length exceeds  the size  of the
       drive's buffers,  the WRITE  BUFFER command  terminates
       with  a   CHECK  CONDITION   status  and   an   ILLEGAL
       REQUEST/Illegal Field  in CDB (05h/24h) sense key/error
       code.

  LXT-200S Family Product Specification & OEM Technical Manual
WRITE LONG - EAh/3Fh
  LXT-200S Family Product Specification & OEM Technical Manual
                                             WRITE LONG - EAh/3Fh


7.28 WRITE LONG - EAh/3Fh

       The WRITE  LONG command  requests the  drive to  perform a
       write operation  of one  data block and the 6 bytes of ECC
       information.  The  data  and  the  6  ECC  bytes  for  the
       specified logical  block are  supplied  by  the  initiator
       during the DATA OUT phase.


7.28.1    SCSI Deviations

       The drive  recognizes either EAh or 3Fh as being the WRITE
       LONG command.   Bytes  7 and 8 of the CDB define the "Byte
       Transfer Length."   If  the data in this field is zero, no
       data is transferred.


7.28.2    Command Parameters

       The CDB  for the  WRITE LONG command is formatted as shown
       in Table 769, WRITE LONG CDB.


                                

                           Table 769
                         WRITE LONG CDB


       The block  address field  specifies the block at which the
       write long operation begins.

       CAUTION:     The physical  location of  the READ  LONG and
       WRITE LONG  block address  is computed  using the physical
       sector size instead of the logical block size.


7.28.3    Error Conditions

       If the LBA is invalid, the drive terminates the WRITE LONG
       command with  a CHECK  CONDITION  status  and  an  ILLEGAL
       REQUEST/Illegal Block  Address (05h/21h)  sense  key/error
       code.
 LXT-200S Family Product Specification & OEM Technical Manual
 LXT-200S Family Product Specification & OEM Technical Manual

       
























































Doc 1018328, Rev B           1            Maxtor Corporation

Doc 1018328, Rev B           1            Maxtor Corporation

 LXT-200S Family Product Specification & OEM Technical Manual


APPENDIX A:  CDB BIT DEFINITIONS

                 Abbreviation Meaning
                 

                 ARRE       automatic    read     reallocation
                 enabled bit
                 AWRE       automatic    write    reallocation
                 enabled bit
                 BytChk     byte check bit
                 DCR        disable correction bit
                 DCRT       disable certification bit
                 DevOfl     device off-line bit
                 DPRY       disable primary bit
                 DT         defective track bit
                 DTE        disable transfer on error bit
                 EEC        enable early correction bit
                 FmtData    format data bit
                 FOV        format options valid bit
                 HSEC       hard sector format bit
                 ILI        incorrect length indicator bit
                 Immed      immediate bit
                 INS        inhibit save bit
                 PCF        page control field bit
                 PER        post error bit
                 PF         page format bit
                 PMI        partial medium indicator bit
                 PS         parameters saveable bit
                 RC         read continuous bit
                 RelAdr     relative address bit
                 RMB        removable media bit
                 SlfTst     self-test bit
                 SP         save parameters bit
                 SS         spare sector bit
                 SSEC       soft sector format bit
                 STPF       stop format bit
                 SURF       surface bit
                 TB         transfer block bit
                 3rdPty     third party reservation bit
                 UntOfl     unit off-line bit
                 VU         vendor unique bit
                 WP         write protect bit















Doc 1018328, Rev B           2            Maxtor Corporation


 LXT-200S Family Product Specification & OEM Technical Manual
 LXT-200S Family Product Specification & OEM Technical Manual

       

 LXT-200S Family Product Specification & OEM Technical Manual


APPENDIX B:  UNITS OF MEASURE

          Abbreviation   Meaning
          

          A/m  amps per meter
          AWG  American wire gauge
          bpi  bits per inch
          dBa  decibel, A-weighted
          fci  flux changes per inch
          g    gram
          Gbyte     gigabyte
          Hz   hertz
          mA   milliamp
          A   microamp
          Mbit megabit
          Mbyte     megabyte
          m   micrometer
          msec millisecond
          sec microsecond
          nsec nanosecond
          Oe   oersted
          RH   relative humidity
          rpm  revolutions per minute
          tpi  tracks per inch
          xxb  binary values
          xxh  hexadecimal values

       
LIST OF ABBREVIATIONS
       ACK.  Acknowledge

       ADR.  Address

       ANSC.  American National Standards Committee

       ANSI.  American National Standards Institute

       async.  Asynchronous

       BCV.  Buffer control valid

       C/C.  Continuous/composite (format)

       CCS.  Common Command Set

       C/D.  CONTROL/DATA signal

       CDB.   Command descriptor  block, the structure used to
       communicate requests from an initiator to a drive.

       cmd.  Command

       CRC.  Cyclic redundancy check

       CSA.  Canadian Standards Association

       DB (7-0, P).  Eight data-bit signals, plus a parity-bit
       signal, that form a DATA BUS.

       DC.  Direct current

       DCR.  Disable error correction

       DMA.  Direct memory access

       EBP.  Erase bypass

       ECC.  Error correction code

       ECL.  Emitter-coupled logic

       EDAC.  Error detection and correction

       EIA.  Electrical Industry Association

       ENDEC.  Encoder/decoder

       EPROM.  Erasable programmable read only memory
       ERA.  Erase all
       FCC.  Federal Communications Commission

       FW.  Firmware

       G.  Constant of gravitation

       gnd.  Ground

       HDA.  Head/disk assembly

       hex.  Hexadecimal

       HW.  Hardware

       I/O.  Input and/or output

       ISG.  Intersector gap

       ISO.  International Standardization Organization

       LBA.  Logical block address

       LED.  Light-emitting diode

       LSB.  Least significant bit

       LSI.  Large-scale integration

       LSTTL.  Low power Schotky transistor-transistor logic

       LUN.   Logical unit number, an encoded 3-bit identifier
       for the logical unit.

       C.  Microcomputer

       computer.  Microcomputer

       MFM.  Modified frequency modulation (encoding)

       MO.  Magneto optics

       P.  Microprocessor

       MSB.  Most significant bit

       MSG.  Message

       MTBF.  Mean time between failures

       MTTR.  Mean time to repair
       N.C.  No connection
       nom.  Nominal

       OEM.  Original equipment manufacturer

       PC.  Polycarbonate

       PCB.  Printed circuit board

       PLL.  Phase-locked loop

       PLO.  Phase-locked oscillator

       PM.  Preventive maintenance

       P/N.  Part number

       POH.  Power On hours

       P-P.  Peak to peak

       PROM.  Programmable read only memory

       ptrn.  Pattern

       RAM.  Random-access memory

       REQ.  Request

       RLL.  Run-length limited

       ROM.  Read-only memory

       rsrv.  Reserved

       R/W.  Read and/or write

       SCSI.  Small Computer Systems Interface

       std.  Standard

       SW.  Software

       sync.  Synchronization, synchronous

       tbd.  To be determined.

       TLA.  Top level assembly

       TTL.  Transistor-transistor logic
       typ.  Typical
       UL.  Underwriter's Laboratories, Inc.

       UNC.  Unified National Coarse

       UNF.  Unified National Fine

       VCO.  Voltage-controlled oscillator

       VDE.  Verband Deutscher Electrotechniker

       WORM.  Write once read multiple

       XFER.  Transfer
       
GLOSSARY

       This glossary  includes definitions  of words  used in the
       text, figures,  and  tables  of  this  manual.    It  also
       includes  some  definitions  of  industry-specific  terms.
       Glossary entries  in all  lower case  are entries  with no
       case-specific meaning.  For example, "assert" has the same
       meaning no  matter  what  the  capitalization.    Glossary
       entries with  some kind of capitalization are entries that
       are incorrect  if any other capitalization is used.  "CDB"
       is an  example of  a  glossary  entry  with  case-specific
       meaning.

       arbitration winner.  The arbitrating SCSI device which has
       the highest SCSI address.

       assert.  A signal driven to the true state.

       bit.  Binary digit

       byte.  Eight consecutive binary digits

       connect.   The function  that  occurs  when  an  initiator
       selects a target to start an operation.

       disconnect.   The  function  that  occurs  when  a  target
       releases control  of the SCSI bus allowing it to go to the
       BUS FREE phase.

       false.  A signal value of zero

       firmware.   Computer programs  encoded permanently  into a
       ROM

       hard error.   An  error which  is not  recoverable by read
       retries, excluding ECC correction.

       initiator.   A SCSI  device, usually  a host  system, that
       requests that  an operation  be performed  by another SCSI
       device.

       INTERMEDIATE status.   A status code sent from a target to
       an initiator  upon completion  of each command in a set of
       linked commands, except for the last command in the set.

       logical thread.   The logical path which exists between an
       initiator's memory  and a  bus device LUN, even though the
       physical path may be disconnected.

       logical unit.   A  physical or  virtual device addressable
       through a target.

       negate.  A signal driven to the false state
       one.  True signal value

       parity.  A method of ensuring the accuracy of byte values

       reconnect.  The function that occurs when a target selects
       an initiator  to continue  an operation  after having been
       disconnected.

       reserved.   Bits, bytes,  fields and  code values that are
       set aside for future standardization.

       SCSI address.  The representation of the unique address (0
       - 7) assigned to a SCSI device.

       SCSI ID.   The  bit-significant representation of the SCSI
       address, referring to one of the signal lines DB (7 - 0).

       status.   One byte of information sent from a target to an
       initiator upon completion of each command.

       target.     A  SCSI  device  that  performs  an  operation
       requested by  an initiator, in this manual, usually a disk
       drive.

       tbd.   To be  determined.  Values which are not defined as
       of the date the manual is published.

       true.  A signal value of one

       vendor unique.   The bits, fields, or code values that are
       vendor specific.

       zero.  False signal value
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