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2.4 COM Port and Interrupt Settings
If your computer is equipped with one or more serial
ports, you will need to change the COM Port setting on the
modem (to either COM 3 or 4), or disable the PC's built-in
COM port.
An IRQ (interrupt request) is a signal generated by an
I/O device that notifies the computer of incoming data. Your
internal modem is capable of accessing IRQs 2, 3, 4, and 5.
I/O devices in your computer cannot share an IRQ with
another device at the same time. Since IRQs can not be
shared at the same time, COM 3 is generally configured to use
IRQ 5, and COM 4 to use IRQ 2. This avoids sharing of IRQs
with COM 1 (IRQ4) and COM 2 (IRQ3).
To change the default COM Port or IRQ settings from
COM 1/IRQ 4 to another setting, locate the Switch Block on
your internal modem (Figure 2-3). Refer to Table 2-1 to
configure the Switch Block to the COM Port and IRQ
Table 2-1 Switch Block Settings
SW-1
Figure 2-3 Switch Block SW-1 Location
COM Port IRQ SW1-1 SW1-2 SW1-3 SW1-4 SW1-5 SW1-6
1 (3F8)
default
4 ON ON OFF OFF ON OFF
2 (2F8) 3 OFF ON OFF ON OFF OFF
3 (3E8) 5 ON OFF OFF OFF OFF ON
4* ON OFF OFF OFF ON OFF
4 (2E8) 2(9)** OFF OFF ON OFF OFF OFF
3* OFF OFF OFF ON OFF OFF
* Use these IRQs only if your software can not address IRQ5 or IRQ2
** When using Windows with the modem set for IRQ2, select IRQ9 in
Control Panel