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8 SFC PROGRAM
8.2 Structure
Series sequence
When the transition becomes TRUE, the active state transitions from the preceding step to the subsequent step.
Selective sequence (divergence/convergence)
A step branches to multiple transitions, and only the step in the line where the transition becomes TRUE first is activated. The
next step is activated when the transition immediately before convergence, which is in the line where the transition becomes
TRUE first, becomes TRUE.
• The selective sequence allows branching to up to 32 transitions.
• If multiple transitions become TRUE simultaneously, the condition to the left will take precedence.
• An SFC diagram in which the number of branches is different from the number of merges in a selective sequence can also
be created. However, in an SFC diagram, selective divergence and parallel convergence or parallel divergence and
selective convergence cannot be combined.
When the transition (2) becomes TRUE while the step (1) is active, the step (1) is
deactivated and the step (3) is activated.
Item Description
Divergence When the step (1) is active, the step whose transition becomes TRUE first is
activated. (When the transition (3) becomes TRUE before (2) becomes TRUE,
the step (5) is activated.)
The step (1) becomes inactive. However, if it is a coil HOLD step [SC], the step
holds the coil output or action according to its attribute.
• If multiple transitions become TRUE simultaneously, the condition to the left
will take precedence.
• Subsequent processing will proceed from step to step in the selected column
until another convergence occurs.
Convergence When the transition (1) or transition (2) on the activated branch becomes
TRUE, the step (5) is activated.
The activated step (3) or (4) becomes inactive. However, if it is a coil HOLD
step [SC], the step holds the coil output or action according to its attribute.
If transition (1) and (2) become TRUE simultaneously, the action of step (3) will
be executed.
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