Function description
APCIe-040
Application example
In a computer system, different tasks (application programs) are monitored.
Task 1 triggers watchdog 0 (reload value = 100).
Task n
Watchdog 0
100 (Reload value)
99
….
50
100 (Reload value)
99
…
0
Trigger
Interrupt,
warning relay is
switched
Task 2
Task 1
If Task 1 is blocked due to a system error, the watchdog trigger is not released and watchdog 0 runs
down. After the watchdog has run down, a yellow warning lamp is switched on via the warning relay.
In the interrupt routine, a diagnostic program is started which analyses the reason for the blocking of
Task 1.
In case the diagnostic program cannot find the reason for the problem during a programmable delay,
the reset relay is switched. This closes the hardware reset contact of the computer system and thus
restarts the computer.
4.2
Digital inputs (24 V
The board
APCIe-040
has seven digital inputs over which watchdogs can be triggered or timers can be
started or stopped (see Fig. 4-1).
Table 4-1: Function range for each input
Function
Meaning
Options
Watchdog trigger
Triggers the watchdog.
Reacts to “0” and/or to “1”
(24 V) at the input.
Timer gate
Starts or stops the timer.
Reacts to “0” and/or to “1”
(24 V) at the input.
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