SBC PCD2.M5 Series - Software Watchdog

Hardware Manual for the PCD2.M5 Series│Document 26/856; Version EN 12│2014-07-24
Saia-Burgess Controls AG
Software watchdog
PCD2.M5_ Classic CPUs and expansion housings
3-52
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3.16 Softwarewatchdog
The hardware watchdog provides maximum security. However, for non-critical
applications,asoftwarewatchdogmaybesufcient,wherebytheprocessormonitors
itself and the CPU is restarted in the event of a malfunction or a loop.
The core of the software watchdog is the instruction SYSWR K 1000. When this is
rstissued,thesoftwarewatchdogfunctionisactivated.Thisinstructionmustthenbe
issued at least every 200 ms, or the watchdog will trigger and restart the controller.
Instruction: SYSWR K 1000 ;Softwarewatchdoginstruction
R/K x ;Parametersaspertablebelow
;Kconstantorvaluein
;register
x = 0 The software watchdog is deactivated
x = 1 Thesoftwarewatchdogisactivated;iftheinstructionisnot
repeated within 200 ms, there will be a cold start
x = 2 Thesoftwarewatchdogisactivated;iftheinstructionisnot
repeatedwithin200ms,XOB0willbecalledandthenthere
will be a cold start
XOB0callsareenteredinthePCDhistoryasfollows:
"XOB0WDOGSTART" whereXOB0hasbeeninvoked
by the software watchdog
"XOB0STARTEXEC" whereXOB0hasbeeninvoked
because of a supply fault