Interrupt Operation - ICP DAS USA PIO-D64 User Manual

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2.7

Interrupt Operation

There are three interrupt sources in PIO-D64/PIO-D64U. These three
signals are named as INT_CHAN_0, INT_CHAN_1 and INT_CHAN_2. Their
signal sources are given as follows: (Refer to Sec. 2.5 for the source of
interrupt signal)
INT_CHAN_0: EXTIRQ
INT_CHAN_1: EVTIRQ
INT_CHAN_2: TMRIRQ
If only one interrupt signal source is used, the interrupt service routine
does not have to identify the interrupt source. Refer to DEMO3.C, DEMO4.C
and DEMO5.C of DOS operating system for more information.
If there are more than one interrupt source, the interrupt service routine
has to identify the active signals as follows: (refer to DEMO6.C of DOS
operation system)
1. Read the new status of all interrupt signal sources(refer to Sec 3.1.5)
2. Compare the new status with the old status to identify the active signals
3. If INT_CHAN_0 is active, service it
4. If INT_CHAN_1 is active, service it
5. If INT_CHAN_2 is active, service it
6. Update interrupt status
Note that if the interrupt signal is too short, the new status may be as same
as old status. In that condition the interrupt service routine can not identify which
interrupt source is active. So the interrupt signal must be hold_active long
enough until the interrupt service routine is executed. This hold_time is different
for different operating system. The hold_time can be as short as micro-second
or as long as second. In general, 20 ms is enough for all operating system.
PIO-D64/PIO-D64U User's Manual ( Ver.1.6, Mar. 2015, PMH-007-16 ) ----- 17