PEX/PIO/PISO-DA Series Card
Analog Output Boards
User Manual/ Ver. 3.1/ Oct. 2013/ PMH-0010-31/ Page: 14
2.3
Interrupt Operation
There are two interrupt sources included in the PEX-DA and PIO/PISO-DAxU series. These
two signals are named as INT0 and INT1, and their signal sources are as follows:
INT0: 8254 counter0 output (Refer to
INT1: 8254 counter2 output (Refer to
If only one interrupt signal source is used, the interrupt service routine doesn’t have to
identify the interrupt source. Refer to DEMO3.C and DEMO4.C for more information.
If there is more than one interrupt source, the interrupt service routine has to identify the
active signals in the following manner: (Refer to DEMO5.C and DEMO6.C)
1.
Read the new status of all interrupt signal sources
2.
Compare the new status with the old status to identify the active signals
3.
If INT0 is active, service it
4.
If INT1 is active, service it
5.
Save the new status to replace the old status
Note:
If the interrupt signal is too short, the new status may be the same as the old status. In
that situation, the interrupt service routine will not be able to identify which interrupt
source is active, so the interrupt signal must be hold_active for long enough until the
interrupt service routine is executed. This hold_time is different for different OS versions.
The hold_time can be as short as a micro-second or as long as second. In general, 20 mS
should be long enough for all OS version.
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