Manual PCI-DIO-48JP/JPS
17
INTERRUPT EXAMPLES
A rising edge with at least a microsecond hold time will be latched if the IEN jumper is in place and if any
address decoded by the board has been read or written to. Interrupts are disabled on ‘power up’. An
interrupt service routine may clear all interrupts from the board by writing any value to Base Fh.
Example 1:
Internal interrupt (generated by software)
The interrupt option jumper for the group must be in the IEN position. Configure port C Low as an output
and set bit C3 low. Enable interrupts globally by writing to Base Bh. Toggle bit C3 high for at least
1 uS then low. Note that this pulse will show up at pin 5 or 41 of the connector.
Example 2:
External
interrupt
The interrupt option jumper for the group must be in the IEN position. Configure port C Low as an input and
enable interrupts globally by reading any address decoded by the board. The pulse at pins 9 or 59 (bit C3)
must go high for at least 1 uS then low.
Example 3:
Gating the external interrupt
An open-collector (or open-drain) driver must connect to pin 5 or 41 to avoid contention (this is critical).
Write 0XXX (where X is ‘don’t care’) to port C Low. To gate the external interrupt ‘off’ configure port C Low
as an output (don’t change the value of the most significant bit). To gate the external interrupt ‘on’ configure
port C Low as an input.
