Step Transition Watchdog Timer - Mitsubishi Electric MELSEC-Q Series Programming Manual

4.6

Step Transition Watchdog Timer

The step transition watchdog timers are timers that measure the time from the point when the relevant step is placed in the
execution status until the point when a transition to the next step occurs.
If a transition from the relevant step to the next step fails to occur within the designated time period, the preset annunciator (F)
will be turned ON.
• When using the step transition watchdog timer, set the "set time" and the "device number of annunciator (F) that will turn
ON at time-out" to the special register for step transition watchdog timer setting (SD90 to SD99). The step transition
watchdog timer starts timing when the special relay for step transition watchdog timer start (SM90 to SM99) is turned ON in
the operation output of the step that performs a time check. When any corresponding one of SM90 to SM99 is turned OFF
during timing, the step transition watchdog timer stops timing and is reset.
• There are 10 step transition watchdog timers, watchdog timer 1 to watchdog timer 10, in the whole SFC program. The
special relay for step transition watchdog timer start and the special register for step transition watchdog timer setting are
assigned to each watchdog timer as indicated below.
Watchdog Watchdog
Timer 1 Timer 2
Special SM90 SM91
relay
Special SD90 SD91
register
• The method of setting to SD90 to SD99 is as shown below.
• When the parameter where the "High speed interrupt I49 fixed scan interval" has been set is written to the
High Performance model QCPU whose first five digits of serial No. are "04012" or later, the step transition
watchdog timers cannot be used. No processing is performed if the step transition watchdog timers are
executed.
• The step transition watchdog timers are not available for the Basic model QCPU, Universal model QCPU,
and LCPU.
Watchdog Watchdog Watchdog
Timer 3 Timer 4 Timer 5
SM92 SM93 SM94
SD92 SD93 SD94
Watchdog Watchdog Watchdog
Timer 6 Timer 7 Timer 8
SM95 SM96 SM97
SD95 SD96 SD97
4 SFC PROGRAM CONFIGURATION
4.6 Step Transition Watchdog Timer
4
Watchdog Watchdog
Timer 9 Timer 10
SM98 SM99
SD98 SD99
117