Mitsubishi Q Series Programming Guide

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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
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.
(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
Timer 1
Watchdog
Timer 2
Watchdog
Timer 3
Watchdog
Timer 4
Watchdog
Timer 5
Watchdog
Timer 6
Watchdog
Timer 7
Watchdog
Timer 8
Watchdog
Timer 9
Watchdog
Timer 10
Special
relay
SM90 SM91 SM92 SM93 SM94 SM95 SM96 SM97 SM98 SM99
Special
register
SD90 SD91 SD92 SD93 SD94 SD95 SD96 SD97 SD98 SD99
(3) The method of setting to SD90 - SD99 is as shown below.
Time setting
(1 to 255 (setting value 1 s))
b0
b7
b15 b8
Annunciator (F) (ON when time-over
status occurs) device No. setting (0 to 255)
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 cannot be used in the Basic model QCPU and
Universal model QCPU..

Mitsubishi Q Series Specifications

General

Brand	Mitsubishi
Model	Q Series
Category	Control Unit
Language	English