MaxTech 28, 800 user manual SW1 Settings, Devices in your computer cannot share an IRQ with

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 combination needed for your application. Any time the

COM or IRQ setting for the modem is changed, the settings in the software must be changed to match.

Figure 2-3 Switch Block SW1 Location

SW1

Table 2-1 SW1 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 IRQ 5 or IRQ 2

**When using Windows with the modem set for IRQ2, select IRQ9 in Control Panel

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