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6 SFC PROGRAM EXECUTION
MELSEC-Q
(1) Operation at program change made by write to PLC
(a) When program was written with CPU module in PAUSE/STOP status
1) Program start after write to PLC
An initial start is performed independently of the SFC start mode setting (initial
start/resume start).
Depending on the SFC program change, however, an initial start is not made but a
resume start may be made at the resume start setting.
Refer to Section 4.7.1 for details of the SFC program start mode.
2) Device status at program start
At a program start after write to PLC, the CPU module devices operate as described in
the following table depending on the setting of the SFC device clear mode setting flag
(SM326).
Operation
SM326
Step relay Other than step relay
OFF Turned ON/OFF by the system.
SFC program is executed after all
devices have been cleared.
ON Turned ON/OFF by the system.
SFC program is executed with all devices
held.
POINT
The setting of SM326 is valid only when an SFC program exists after write to PLC.
When sequence program and/or parameter write is performed, the setting of
SM326 is also valid.
(The setting of SM326 is ignored when only the data other than the SFC program,
sequence program and parameters are written.)
(b) When program was written with CPU module in RUN status
1) Program start after write to PLC
An initial start is performed independently of the SFC start mode setting (initial
start/resume start).
Refer to Section 4.7.1 for details of the SFC program start mode.
2) Device status at program start
The SFC program is executed with all devices held.
(2) Program change by online change
(a) Program start after write to PLC
When program change is made by online change, a resume start is performed
independently of the SFC start mode setting.
(b) Device status at program start
The SFC program is executed with all devices held.
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