### Interrupt Request Line (IRQ) Requirements

#### PCI Adapters

An IRQ will be assigned by the PCI BIOS. It should be noted that not all device drivers require an IRQ.

It is important to keep in mind that some older ISA products may have interrupts set by switches or jumpers which may go undetected by the PCI BIOS.

If you are having difficulties with your installation, be sure to verify that your Digi PCI adapter has not been assigned an IRQ that is already being used by another adapter.

#### ISA Adapters

Depending upon the operating system or environment, it may be necessary to assign an IRQ (Interrupt Request) line to the adapter.

Digi adapters can be set to use IRQs 3, 5, 7, 10, 11, 12 or 15, or IRQs can be disabled (some Digi device drivers do not use IRQs). The IRQ selection is programmed into the adapter by the device driver. No switches or jumpers are required to change the IRQ selection.

When run with an IRQ enabled (such as with Windows), the IRQ chosen for the adapter must be unique--that is, no other adapter or device can have the same IRQ assigned to it.

The most common sources of contention for IRQs are:

IRQ3: Used by standard serial ports COM2 and COM4, if present.

IRQ5: Used by secondary parallel printer port, if present.

IRQ7: Used by primary parallel printer port, if present.

Many different expansion adapters use IRQs. Check the documentation for the adapters installed in your computer to see which, if any, IRQs they may be using.

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