Mitsubishi QCPU (Q Mode), Руководство пользователя

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MELSEC-Q
7 FUNCTION
7.14 Watch dog Timer (WDT)
(1) What is Watch dog Timer (WDT)?
(a) The watch dog timer is an internal sequence timer to detect High
Performance model QCPU hardware and sequence program error.
(b) When the watch dog timer expires, a watch dog timer error occurs.
The High Performance model QCPU responds to the watch dog timer error
as follows:
1) The High Performance model QCPU turns off all outputs.
2) The front-mounted RUN LED turned off, and the ERR. LED starts
flicking.
3) SM1 turns ON and the error code is stored in SD0.
(c) The default value of the watch dog timer is 200 ms.
The setting range is 10 to 2000 ms (in 10ms units).
(2) Watch dog Timer Setting and Reset
(a) The watch dog timer setting can be changed at the "PLC RAS" tab screen
in the “(PLC) Parameter" dialog box.
(b) High Performance model QCPU resets the watch dog timer during the END
processing.
1) When the END/FEND instruction is executed within the set value of the
watch dog timer in the sequence program and the High Performance
model QCPU is operating correctly, the watch dog timer does not time
out.
2) When the scan time of a sequence program is extended due to the
High Performance model QCPU hardware error or execution of
interrupt program/fixed scan execution type program, and END/FEND
instruction cannot be executed within the set watch dog timer value,
the watch dog timer times out.
(3) Precautions
(a) An error of 0 to 10 ms occurs in the measurement time of the watch dog
timer. Set the watch dog timer for a desired value by taking such an error
into account.
(b) The watch dog timer is reset with the WDT instruction in the sequence
program. If the watch dog timer expires while the FOR and NEXT
instructions are repetitiously executed, reset the watch dog time with the
WDT instruction.
FOR K1000
WDT
M0
NEXT
WDT reset
Program for repetition processing
Repetition
(1000 times)