Omron WS02-CXPC1-V8 - V8.1 REV 02-2009 Operation Manual page 61

Elements of SFC
Initial Step
An initial step is the step that unconditionally becomes active upon program execution
start. All other steps are inactive at this moment.
It is also the first step to be executed in the SFC chart.
When the initial step becomes active, the actions defined in the initial step are
executed.
The initial step is represented as shown below.
• Only one initial step can be created within an SFC chart.
• The initial step does not necessarily need to be positioned at the head of the
program.
• An initial step can hold one or many action blocks.
• When the initial step becomes active, action blocks assigned to the step are
executed.
If the power supply is turned OFF during SFC program execution. The program will be
executed from the initial step when the power supply is turned back ON. To perform
initialization when continuing operation or to select the steps with the step control
instructions to continue step operation, include status control programming in the initial
step.
Normal Step
A normal step is the step that becomes active if the transition condition is met.
When the step becomes active, the actions defined in the normal step are executed.
The normal step is represented as shown below.
• There is no limit on the number of normal steps used within an SFC chart.
• A normal step can hold one or many action blocks.
• When a normal step becomes active, action blocks assigned to the step are
executed.
Subchart Step
A subchart step is the step that calls up the subordinate SFC chart (subchart) from an
SFC chart.
The subchart step is represented as shown below.
Subchart 1
A subchart is the macro expansion of an SFC step into a group of SFC programs,
similar to the subroutine of a conventional programming language.
Step 1
Step 1
Step 1
Section 2-3
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