IBM 56K Modem, Installation Manual

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56K Modem Internet Kit
6-9
9 Reserved
10 Reserved
11 Reserved
As you can see above, there are no default assignments for COM3 and
COM4. In order to use COM3 or COM4, you must assign it to an IRQ. This
means sharing that IRQ with it's default assignment. This is possible, ONLY
if the default assignment is NOT in use. For example, you can assign COM3
to IRQ5, if you are not using LPT2 for a second printer, or other external
parallel device. You CAN NOT assign COM4 to IRQ2 because IRQ 2 is
being used by the computer for a mandatory function. If you have a mouse
attached to COM1, IRQ4 is in use by COM1 and can not be used for COM3.
If you plan to use COM3 or COM4, you must assign these COM Ports to an
IRQ through Windows. Before running your software, you must first re-install
your modem with the right IRQ and COM Port settings.
AT Commands
The full list of AT commands is provided in the readme file located on the
56K Modem installation diskette. AT commands can be issued to the modem
in a terminal mode from programs such as Hyperterminal in Windows 95/98
or Terminal in Windows 3.1. Or they can be set up in communication
software such as Internet dialer programs as initialization strings. Refer to
your communication software documentation if this is required. The most
commonly used AT command is to reset the modem to it’s factory settings
(ATZ3) or to set it to it’s factory settings without resetting it (AT&F0).
When putting AT commands in communication software initialization
strings, the “AT” prefix may not be required (Z3 instead of ATZ3, for
example).