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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
(3) When a coil ON status (at coil HOLD step) has been maintained to the next step, the coil will
be switched OFF at any of the following times:
(a) When the end step of the corresponding block is executed. (Except when SM327 is ON)
(b) When an SFC control instruction (rBLm) designates a forced END at the block in question.
(c) When an SFC control instruction (rBLm\Sn, rSn) designates a reset at the block in question.
(d) When a reset occurs at the device designated as the SFC information register's block
START/END device.
(e) When a reset step for resetting the step in question becomes active.
(f) When the SFC START/STOP command (SM321) is switched OFF.
(g) When the coil in question is reset by the program.
(h) When the STOP instruction is executed with the stop-time output mode OFF.
(i) When S999 is designated at the reset step in the corresponding block.
(4) Block STOP processing
Make a block STOP using the STOP/RESTART bit of the SFC information devices or the
block STOP instruction of the SFC control instructions.
The processing of the active step in the block where a block STOP was made is as described
below.
(a) When the "block STOP-time operation output flag (SM325)" is OFF (coil output OFF)
• The step becomes inactive when the processing of the corresponding block is performed
first after a block STOP request.
• All coil outputs turn OFF.
However, the coils turned ON by the SET instruction remain ON.
(b) When the "block STOP-time operation output flag (SM325)" is ON (coil output held)
The coil outputs remain ON during a block STOP and after a block RESTART.
(5) Precautions when designating coil HOLD steps
(a) PLS instruction
When the execution condition of the PLS instruction is satisfied and the transition condition
is satisfied at the same scan where the PLS instruction was executed, the device turned
ON by the PLS instruction remains ON until the OFF condition in above (3) is satisfied.
(b) PLF instruction
When the execution condition of the PLF instruction is satisfied and the transition condition
is satisfied at the same scan where the PLF instruction was executed, the device turned
ON by the PLF instruction remains ON until the OFF condition in above (3) is satisfied.
(c) Counter
If the count input condition turns ON/OFF after a transition to the next step, the counter
does not start counting.
(d) Timer
When a step transition occurs after the transition condition is satisfied with the coil of the
timer ON, the timer stops timing and holds the then present value.
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