Modem User's Manual

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