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

4 SFC PROGRAM CONFIGURATION

4.6 Step Transition Watchdog Timer

The step transition watch dog 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.
(1) 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.
(2) 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
relay
Special
SD90
register
(3) The method of setting to SD90 - SD99 is as shown below.
b15
POINT
(1) 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.
(2) The step transition watchdog timers are not available for the Basic model QCPU, Universal
model QCPU, and LCPU.
4 - 84
Watchdog Watchdog
Timer 3 Timer 4
SM91 SM92 SM93
SD91 SD92 SD93
b8 b7
Watchdog Watchdog Watchdog
Timer 5 Timer 6 Timer 7
SM94 SM95 SM96
SD94 SD95 SD96
b0
Time setting
(1 to 255 (setting value 1 s))
Annunciator (F) (ON when time-over
status occurs) device No. setting (0 to 255)
Watchdog Watchdog Watchdog
Timer 8 Timer 9 Timer 10
SM97 SM98 SM99
SD97 SD98 SD99
4 - 84