Technical description Chapter 8
APCI-/CPCI-1500
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8.2.4 Counter/timer
On the board three 16-bit counters/timers are available in the component Z8536
(downwards counting). Each counter/timer can be programmed by software.
If the component Z8536 operates as a counter, the corresponding inputs
are used as follows:
Counter
Counter 1:
Input 14
signal input
.
Counter 2:
Input 10
signal input
Input
11
can be used as a "trigger" function
Input 12
can be used as a "gate" function.
Counter 3
Input 15
signal input
Input
16
can be used as a "gate" function.
Timer
If the component Z8536 is used as a timer, the frequency is used as a reference.
"Gate" and "trigger" are possible through the inputs.
Gate :
can be driven by software or an input can be set. The polarity of the input can
be programmed. This "gate" stops counting when it is set.
Trigger :
can be driven by software or an input can be set.
The polarity of the input can be programmed. This "trigger" re-loads the
counter/timer with the initial counter value.
The following functionalities are available:
- Initialising the counters/timers,
- Starting the counters/timers,
- Stopping the counters/timers,
- Reading the counter value of the counters/timers
The counter/timer 3 has a special function:
Watchdog Timer
.
The function
Watchdog Timer
allows to supervise the software or PC.
The principle is:
The counter/timer 3 is programmed as a non reloadable timer.
The timer is started. The outputs are reset when the timer has run down
(switch OFF).
The user software must be built in such a way that the output channels are
always set to "ON" again.
You thus avoid that the watchdog runs down.
