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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
4.2.8 Block START step (with END check)
A block START step (with END check) is the step where the specified block is started, and when
the START destination block is then deactivated, the check of the transition condition to the next
step is started.
(1) The operation of the block START step (with END check) is described below.
(a) When activated, the block START step (with END check) starts the specified block.
(b) No processing is performed until the START destination block is deactivated after its
execution has ended.
(c) When the START destination block is deactivated after its execution has ended, only the
transition condition check is performed.
(d) When the transition condition is satisfied, a transition to the next step occurs.
Block m
Bm
(2) A simultaneous start cannot be made for a single block.
The block that has already started cannot be started, either.
If either of the above starts is made, the following processing is performed depending on the
setting of the operation mode at block double START. *1
(Refer to Section 4.7.5 for details of the operation at block double START.)
(a) When the setting of the operation mode at block double START is "STOP"
A "BLOCK EXE. ERROR" (error code: 4620) occurs and the CPU module stops
processing.
(b) When the setting of the operation mode at block double START is the default setting of
"WAIT"
Processing is not performed and waits until the START destination block ends its execution.
POINTS
*1: The Basic model QCPU and Universal model QCPU does not allow the setting of the
operation mode at block double START.
For the Basic model QCPU and Universal model QCPU, the operation mode at block
double START is "WAIT" only.
(3) A block START request can start multiple blocks simultaneously by performing a parallel
transition (refer to Section 4.3.3).
The steps in the simultaneously started blocks are processed in parallel.
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