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8 SFC PROGRAM
8.2 Structure
• The following shows how to restart the block once ended.
• An action cannot be created to the end step.
• The setting of SM327 (Output mode at execution of the END step) is valid only when the end step becomes active. When a
forced termination is performed by the SFC control instruction (Ending a block) or the like, the coil outputs of all steps are
turned off.
• If only the HOLD steps that hold operations remain when the end step becomes active, those steps are deactivated even
though SM328 (Clear processing mode when the sequence reaches the END step) is on. If it is not required to turn off the
coil outputs of the HOLD steps that hold operations, turn on SM327. The following figure shows the operational relationship
between SM328 and the coil HOLD step [SC].
• If a block is started at the block start step when SM328 is on, execution returns to the source as soon as there are no active
step that does not hold the operation in the block.
• When "FX3 compatible transition operation mode setting" is set to "Enable", the CPU module is powered off and on, or
SM328 is turned on at reset.
Multiple end steps can be created in the SFC diagram.
To do so, select a step in the selection branch and select [Edit] [Modify] [End Step/Jump] from the menu.
Item Description
Block 0 "Start Conditions Setting" is set to "Auto-start
block 0" in the SFC Setting of parameters.
The initial step is automatically activated again and processing is executed repeatedly.
"Start Conditions Setting" is set to "Do not auto-
start block 0" in the SFC Setting of parameters.
The block is restarted when a start request is issued for the specified block in the following
methods.
• The block start step is activated by another block.
• The SFC control instruction (Starting a block) is executed.
All blocks other than block 0
When a normal active step remains or when a coil HOLD step
[SC] whose transition has not become TRUE remains (the step
does not hold an operation)
When an active step that holds an operation remains
• When SM328 is off, the block is ended by clearing the step.
• When SM328 is on, processing is continued without clearing the step.
The block is ended by clearing the step regardless of the setting of SM328.
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