MaxTech V.32bis, V.42bis user manual COM Port and Interrupt Settings

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

Figure 2-3 Switch Block SW-1 Location

SW-1

Table 2-1 Switch Block Settings

COM Port	IRQ	SW1-1	SW1-2	SW1-3	SW1-4	SW1-5	SW1-6
1 (3F8)	4	ON	ON	OFF	OFF	ON	OFF
default
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

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