Operation Hold Step (Without Transition Check) - Mitsubishi MELSEC-Q Series Programming Manual

4 SFC PROGRAM CONFIGURATION

4.2.5 Operation HOLD step (without transition check)

An operation HOLD step (without transition check) is a step where the operation output
processing of the corresponding step continues after a transition to the next step.
However, transition processing to the next step is not executed if the transition condition is
satisfied again at the corresponding step.
(1) During normal SFC program operation, the coil ON status (switched ON by OUT instruction
when transition condition is satisfied) is automatically switched OFF before proceeding to the
next step.
When an operation output step is designated as an operation HOLD step (without transition
check), the corresponding step will remain active after a transition to the next step, and
operation output processing will continue.
Therefore, when the input condition changes, the coil status also changes.
[When transition from step n to step (n+1)
occurs with Y10 ON]
Transition
(2) The transition conditions have been satisfied, so no transition condition check is performed
after the next step becomes active.
Therefore, no step transition (subsequent transition) will occur even if the transition conditions
for the relevant step are satisfied again.
(3) An operation HOLD step (without transition check) becomes inactive when any of the following
occur:
(a) When the END step of the block in question is executed.
(b) When an SFC control instruction (RST BLm) designates a forced END at the block in
question.
(c) When the corresponding step is reset by the SFC control instruction (RST BLm\Sn, RST
Sn). (Except when SM327 is ON)
(d) When the device designated as the block START/END device of the SFC information
devices is reset.
(e) When a reset step for resetting the step in question becomes active.
(f) When "S999" is designated at the reset step in the same block.
(g) When the SFC START/STOP command (SM321) is switched OFF.
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X1
n
SE
(ON)
Y10
n+1
(ON)
Remains ON after
transition to step (n+1).
SE
[When X1 turns OFF after transition to
step (n+1)]
SE
Y10
(ON)
X1:OFF
No subsequent
transition
Step activated by
transition condition
being satisfied
SE
X1
n
Y10
(OFF)
(OFF)
Y10
n+1
(OFF)
When X1 turns OFF, Y10 also turns OFF
since processing is being performed after
transition to step (n+1).
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