Irq Selection; Figure 2 - Header E11 And E12, Irq Selection - Omega Engineering ISA RS-422 User Manual

IRQ Selection

Headers E11 and E12 select the interrupt request for each serial port. If COM1: is
selected, the corresponding jumper must be on the IRQ4 setting. If COM2: is
selected, the corresponding jumper must be on IRQ3.
Note: Most communications software applications default COM3: to IRQ4 and
COM4: to IRQ3. This requires the sharing of interrupts between COM1:
and COM3:, and between COM2: and COM4:. While this is the default, it
is not always the preferred setting. Check your software configuration
instructions to determine the most appropriate IRQ selection.

Figure 2 - Header E11 and E12, IRQ Selection

Any two or more ports can share a common IRQ by placing the jumpers on the
same IRQ setting at header E11 and E12 and setting the appropriate selections at
E5 and E6. Note that a polling type driver is needed to share interrupts in this
fashion. Windows does not supply a polling type driver. Consult your particular
software for IRQ selection. If no interrupt is desired, remove the jumper.
OMG-ULTRA-SIO
Card Setup
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