messydisk.device() Amiga Programmer's Manual messydisk.device() ›1mSYNOPSYS ›0m#include #include #include OpenDevice("messydisk.device", Unit, IOExtTD, Flags); BeginIO(IOExtTD); CloseDevice(IOExtTD); ›1mUSAGE ›0mMessydisk.device can be used instead of trackdisk.device. All current trackdisk.device commands are supported. The only functional difference is the format of the disk, which is compatible with messydos systems. ›1mCOMMANDS ›0mSupported commands are: = CMD_INVALID = CMD_RESET * CMD_READ * CMD_WRITE * CMD_UPDATE = CMD_CLEAR = CMD_STOP = CMD_START = CMD_FLUSH TD_MOTOR = TD_SEEK * TD_FORMAT TD_REMOVE TD_CHANGENUM TD_CHANGESTATE TD_PROTSTATUS TD_RAWREAD TD_RAWWRITE TD_GETDRIVETYPE TD_GETNUMTRACKS = TD_ADDCHANGEINT = TD_REMCHANGEINT * ETD_WRITE * ETD_READ ETD_MOTOR = ETD_SEEK * ETD_FORMAT * ETD_UPDATE = ETD_CLEAR ETD_RAWREAD ETD_RAWWRITE The commands marked with * are handled in its own format by messydisk. The commands marked with = are handled by messydisk in the same way as trackdisk supposed is to do. The other commands are sent straight through to trackdisk and are subject to all its flaws and features. ›1mOPENDEVICE FLAGS ›0mTDF_ALLOW_NON_3_5: Allows opening 40 track drives. Ignored, since it is the default behaviour which cannot be disabled. ›1mIO REQUEST FLAGS ›0mThe io_Flags field of an IOStdReq or IOExtTD structure may contain the following flags: IOF_QUICK: This flag is supported for only a few commands. IOTDF_INDEXSYNC: For ETD/CMD_RAWREAD and _WRITE. IOMDF_40TRACKS: This flag is for ETD/CMD_READ, _WRITE, _FORMAT, and _SEEK. If set, treat the disk as 40 cylinder media. If it happens to be in an 80 cylinder drive, every other cylinder will be skipped to use the same cylinders a 40-cylinder drive would. Normally you set or clear this flag once at the time you read the bootblock and examine its layout information. It is guaranteed that messydisk won't change this flag. IOMDF_40TRACKS is not supported for ETD/TD_RAWREAD and _RAWWRITE, since these are considered to KosmoSoft -1- Version 34.5 messydisk.device() Amiga Programmer's Manual messydisk.device() be "diagnostic" functions and therefore should be as raw as possible. ›1mDISK FORMAT ›0mThe disk format used is compatible with messydos systems. Both 40 and 80 cylinder media are supported. There are normally 9 sectors per track and two tracks per cylinder. (Outdated) single-sided disks can only be read if the driving software is prepared to treat them as normal double-sided disks, and skip the sides that are not actually present. On the other hand, the number of sectors per track may vary from 8 to 10. If the number of sectors is different from the default value (9), then track 0 on side 0 must be read first before this is recognized. It is then assumed that all tracks on the entire disk have the same number of sectors. So, all position calculations are based on the layout of the very first track. --- Index pulse ------------------------------------. | 60 * $4e GAP 1 ($9254 encoded) | | --- First Sector -----------------------------. | | | 12 * $00 GAP 2 ($AAAA encoded) | | | 3 * $a1 SYNC ($4489 encoded) | | | | | | 1 * $fe ID-Address Mark -. ($5554) | | | track | | | | side | | | | sector > ID | | | length (0=128,1=256,2=512 etc.)| Field | S | -> CRC 1 | | e | T -> CRC 2 -' | c | r > t > a 22 * $4e GAP 1 ($9254 encoded) | o | c 12 * $00 GAP 2 ($AAAA encoded) | r | k | 3 * $a1 SYNC ($4489 encoded) | | | | | | 1 * $fb DATA-Adress Mark -. ($5545) | | | 512 bytes data > DATA | | -> CRC 1 | Field | | -> CRC 2 -' | | | | | | 80 * $4e GAP 3 ($9254 encoded) | | ----------------------------------------------' | | ...... 8 more sectors ....... | | rest $4e ($9254 encoded) | -----------------------------------------------------' ›1mDEVIATIONS ›0mThe TD_REMCHANGEINT command works. (It doesn't with the 1.2 or 1.3 trackdisk.device). KosmoSoft -2- Version 34.5 messydisk.device() Amiga Programmer's Manual messydisk.device() The messydisk Unit structure does not look like TDU_PublicUnit at all. In some situations, error returns may be different or less specific. Data buffers to be read or written currently don't need to be in Chip memory. This might change in the future. For future compatibility and with the trackdisk.device you should not depend on this. In order to be able to format a track with a nonstandard number of sectors (from 8 to 10), you must use the TD_FORMAT command with less than 40 sectors (20480 bytes) at a time. Since you must always format entire tracks at a time, this uniquely determines the number of sectors you want on each track. The current number of sectors per track, which will be used later when reading from the same disk, is updated accordingly. If you specify 40 sectors or more, messydisk.device does not attempt to guess what you want but simply uses the value that was already set. So, you may choose to first format a single track to indicate the desired number of sectors per track, and then in one call format the entire rest of the disk. When a disk with more or less than 9 sectors per track is read, you must first issue a CMD_READ command for the first sector(s) of the disk. When track 0 is read, messydisk.device determines how many sectors there are on a track. This number is then used afterwards when calculating the tracks and sides of other sectors. So, this is very important. But for those (virtually impossible) cases where not all tracks have the same number of sectors, all sectors that were read on any track will be written back. Fortunately, all currently known file systems have a bootblock at track 0, side 0, so they all adapt transparently. ›1mCAVEATS ›0mThe (outdated) TD_REMOVE command is routed to trackdisk. As a result of this, only one disk remove interrupt (per unit) may be installed (with this command), whether through trackdisk or messydisk. (This seems to have been the original intention of TD_REMOVE.) Of course, current programs should use TD_ADDCHANGEINT. ›1mUTILITIES ›0mA separate program called Ignore is supplied, which may suppress the CRC check in any currently open unit. When the unit is definitively closed and later reopened, ignoring CRC mismatches again has its default value of No. Usage: ignore If you only give the unit number, ignore will output either Yes or No, reflecting whether CRC mismatches currently are ignored. KosmoSoft -3- Version 34.5 messydisk.device() Amiga Programmer's Manual messydisk.device() This program can be useful when you wish to recover data from a damaged or marginal disk. Sometimes text files may be usable even if there are a few errors in them. ›1mAUTHORS ›0mMessydisk is written by ›3mSourcerer ›0mOlaf ›3mRhialto ›0mSeibert. The low-level writing part was originally done by Werner Gόnther. Used with permission. KosmoSoft -4- Version 34.5