Impulse 3440 - Manual (Page 8)

Card Setup
Sealevel Systems ULTRA COMM+422 Page 5
Interrupt Modes
Headers J1A through J4A select the interrupt modes 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. ‘M’ indicates the inclusion of a 1K ohm pull-down resistor required on one
port when sharing interrupts.
N M S
J1A
Figure 4 - Header J1A, 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
ULTRA COMM+422 or a compatible adapter in a bus you should only have
one port set to ‘M’. The following example shows two ports sharing a single
IRQ.
J1A
N S M
J2A
N S M
Figure 5 - Header J1A & J2A, Shared IRQ Mode
Set the jumper to ‘S’ if you are using more than one ULTRA COMM+422 in a
bus or to completely remove the pull-down resistor for hardware compatibility.
Setting the adapter in this configuration when it is not accompanied by a
pull-down resistor will prevent the ports from triggering an interrupt.