
Internal Modem Setup

There are several steps that you can take to ensure that you are not conflicting
with another device or port.

Make sure how many serial ports are on the machine without the modem installed. 
If there are two, make note of the communications ports that are taken.  If you 
have both COM1 and COM2 before you install the modem, you will not be able to 
install your internal modem on any of the standard serial ports.  The reason for
this is because COM1 and COM2's port addresses are taken, and if you install the
modem card on those slots it will cause a memory conflict between the existing 
communications port and the newly installed modem.  You are also not able to 
install the modem on COM3 or COM4 because they share the IRQ (Interrupt Request)
levels with COM1 and COM2.

There are two solutions to this problem.  The first, which is the more 
difficult, requires you to have the manual or documentation for your computer or
peripheral card in which the existing serial ports reside.  These ports can be 
found directly on the motherboard, on an I/O card, or Super IDE Controller 
(combination hard drive/floppy drive/serial port/parallel port card).  What you 
must do is move the jumper switches for a communications port not used to the 
'DISABLE' position.  This will allow you to place the internal modem card on the
communications port that you had just disabled.

The second method of solving the interrupt problem is to move the modem to a 
communications port address and an interrupt level that is not being used by 
another device or serial port.  In order to do this, you must refer to the 
Sportster User's Guide, Page 2-5.  On this page you will find the jumper 
settings for the internal modem.  In the above scenario, if you have both COM1 
and COM2 present on the system, you can place the jumper switch either on COM3 
or COM4.  The next step is to determine the IRQ level the modem is able to use. 
Available interrupt levels are 2, 3, 4, 5 and 7.  Again, if COM1 and COM2 exist 
on the system, IRQ levels 3 and 4 are both being used (even if a device is not 
currently present on the communications port).  If you have a parallel port 
(printer port), then IRQ7 is being used.  The recommended IRQ level in this case
would be IRQ5, since most systems do not use IRQ5 by default.  Some devices, 
such as a sound card, network card, second parallel port, CD-ROM interface 
cards, tape backup interface cards, and SCSI hard drive controller cards can 
take IRQ5, so if you own one of these cards, check which IRQ level that card is 
using before moving the modem to IRQ5.  If IRQ5 is taken by one of those cards, 
you can elect to move that card to another IRQ level, and place your modem on 
IRQ5, or follow the first solution as outlined above in disabling a serial port.

After you have determined where your modem will be placed, the next step is to 
physically install it into the system.  After it has been installed, you must 
configure your software to the communications port and IRQ level in which you 
have placed the modem.  Normally there is an advanced installation or port 
assignment screen where you can change the address and IRQ level of a serial 
port.  In Windows, it is found in the Main icon, Control Panel, Ports, and then 
in the 'Advanced' section of the selected communications port.  (Note:  This 
change applies to all Windows based telecommunications applications.  Once 
configured here, you can select the communications port in the application 
without looking for an IRQ level to change).  Refer to your software manual if 
you are having trouble locating the serial port configuration screen.  Below are
the default addresses and IRQ levels for COM1-COM4:

COM1:  03F8  IRQ:  4
COM2:  02F8  IRQ:  3
COM3:  03E8  IRQ:  4
COM4:  02E8  IRQ:  3

If you are still having trouble getting a response from your U.S. Robotics 
modem, please contact us at the following numbers for technical assistance:

(708) 982-5151 (VOICE)
(708) 933-5552 or (708) 982-0823 (FAX)

U.S. Robotics Technical Support


