Connect Tech CANPRO CTIM-00043 - Manual (Page 21)

CANpro/104 User Manual
21 www.connecttech.com CTIM-00043 (0.01) 1/15/2010
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Interrupt Sharing
Jumper block J3 also plays a part in the interrupt sharing. PC/104 supports the sharing of an
interrupt between multiple cards. For example, two separate CANpro/104 cards are able to share the
same interrupt across all four controllers. To accomplish interrupt sharing, the following steps must
be taken:
All cards that share the same interrupt, but are not actively asserting an interrupt, must tri-state their
outputs. On CANpro/104 cards, this is accomplished by installing a jumper on the INTshrX jumper
location of each CAN controller(s) you wish to share interrupts.
One 1K Ohm resistor must also be attached to each shared interrupt. With the example of two
CANpro/104 cards, the INTres jumper would be installed on only one of the cards.
NOTE:
CANpro/104 has the capability to tri-state its interrupt outputs and the 1K Ohm resistor is jumper
configurable. Other cards may not be able to share interrupts. Please check the manual for each
card.
The example below has configured both cards to interrupt on IRQ 11. Both controllers will tri-state
their outputs when not driving the interrupt line active. This example assumes that another card in
the stack has enabled the 1K Ohm pull-down resistor. Only one card in the group of cards sharing
the same interrupt should enable a pull-down resistor.
To enable the resistor, simply install a jumper on the INTres jumper location, as shown below.
Please note that the Interrupt Resistor Enable controls the Interrupt Resistor for all shared CAN
controller interrupts on the card. You cannot enable the Interrupt Termination Resistor for one
controller only if both are configured for interrupt sharing.
If a card has interrupt sharing enabled for only one of its controllers, the resistor will only be enabled
on the interrupt of the controller that is sharing interrupts.