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

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.
Coil switched ON by the OUT instruction when the transition condition is satisfied
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. After a transition, therefore, the timer continues timing.
Transition condition check after the next step becomes active
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.
Timing when an operation HOLD step becomes inactive
An operation HOLD step (without transition check) becomes inactive when any of the following occur:
• When the END step of the block in question is executed.
• When an SFC control instruction (rBLm) designates a forced END at the block in question.
• When the corresponding step is reset by the SFC control instruction (rBLm\Sn, rSn). (Except when SM327 is ON)
• When the device designated as the block START/END device of the SFC information devices is reset.
• When a reset step for resetting the step in question becomes active.
• When "S999" is designated at the reset step in the same block.
• When the SFC START/STOP command (SM321) is switched OFF.
Block STOP processing
The following processing is performed when a block STOP request is issued to the corresponding block using the STOP/
RESTART bit of the SFC information devices or the block STOP instruction of the SFC control instructions.
■STOP status timing
A STOP status is established after the block STOP request output occurs, and processing returns to the beginning of the
block in question.
■Coil output
A coil output OFF or HOLD status will be established, depending on the output mode setting at the time of the block STOP
designated in the SFC operation mode. ( Page 123 Output mode at block STOP)
However, an ON status will be maintained for coil outputs which were switched ON by the SET instruction.
• When the transition condition immediately before the corresponding step is satisfied or when the step is
reactivated by a JUMP transition, a transition will occur again when the transition condition is satisfied.
• Double STARTs do not apply to reactivated steps.
4 SFC PROGRAM CONFIGURATION
48
4.2 Steps