Interrupt Modes; Figure 3 - Header E5 & E6, Normal Irq Mode; Figure 4 - Header E5 & E6, Shared Irq Mode - Omega Engineering ISA RS-422 User Manual

Interrupt Modes

Header E5 and E6 selects the interrupt mode for each port. Each port must be set
in the correct mode to insure proper operation.
'N' indicates the ( N )ormal, single interrupt per port mode. ' S' Indicates the
(S)hared interrupt mode, which allows more than one port to access a single IRQ.
Any two or more ports can share a common IRQ by placing the jumpers on the
same IRQ setting and setting the appropriate selections at E1. Consult your
particular software for IRQ selection. If no interrupt is desired, remove the
jumper. 'M' indicates the inclusion of a 1K ohm pull-down resistor required on
one port when sharing interrupts.
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Figure 3 - Header E5 & E6, Normal IRQ Mode
Set the jumpers to 'S' for shared interrupt mode on all blocks sharing an IRQ
except one. Set that port block for ' M'. This provides the pull-down resistor
circuit that makes sharing IRQs possible. If you are using more than one OMG-
ULTRA-SIO or a compatible adapter in a bus you should only have one port set
to 'M'. The following example shows both ports sharing a single IRQ.
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Figure 4 - Header E5 & E6, Shared IRQ Mode
OMG-ULTRA-SIO
N S M
N S M
Card Setup
E5
E6
E5
E6
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