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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
(b) When transition destination is parallel branch
1) When setting is "STOP"
.......If any one of the transition destinations of the parallel branch is active, an error
occurs and the processing of the CPU module stops.
Transition destination
2) When setting is "WAIT"
.......Execution waits until all the transition destination steps of the parallel branch
become inactive.
When the transition destination steps all become inactive, a transition is executed
and all the first steps of the parallel branch become active.
In a WAIT status, the previous step is deactivated.
Transition
conditions
satisfied
Transition
executed
Transition
Inactive
Transition conditions
satisfied
Inactive
(WAIT)
Inactive
All active
WAIT status
Active
Transition condition
satisfied
3) When setting is "TRANSFER"
.......When any one of the transition destination steps of the parallel branch is active, a
transition is executed and the previous step becomes inactive.
Transition condition
satisfied
REMARKS
When the transition destination steps are all inactive, normal transition processing is performed
and all the transition destination steps become active.
POINTS
(1) The operation mode for transition to active step (at step double START) applies to a
transition to be executed when a transition condition is satisfied or to a forced transition set
using the transition control instruction (SET TRn) of the SFC control instructions.
When the step control instruction (SET Sn) of the SFC control instructions is used to issue
a START request to the step that is already active, the request is ignored and the
processing continues.
(2) In the Basic model QCPU and Universal model QCPU, the transition to active step (at step
double START) cannot be set.
The transition to active step (at step double START) in the Basic model QCPU and
Universal model QCPU are executed in the "TRANSFER" mode.
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