Omron SYSMAC CX-Programmer 8.1, Operation Manual

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Elements of SFC Section 2-3
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2-3 Elements of SFC
This section explains the element of SFC.
Initial step: The first step to be made active.
Transition
Boolean variable (Bit)
Boolean address (Bit)
ST expression
Program (Ladder or ST)
Supported
t
JUMP ENTRY: Jump Destination
Action
Boolean variable (Bit)
Boolean address (Bit)
Program (Ladder or ST)
Supported
Can be multiple (Number unlimited).
Jump: Jumps to the destination step
Step
2-3-1 Steps
A step is an element of an SFC program and represents a single process within an
entire process.
Operation of Steps
A step is either active or inactive.
An active step executes the actions defined in that step, while an inactive step does not
execute any actions until it becomes active.
The step status transfers when the transition condition is met, but the transfer actually
depends the status of the step before the transition as well as the transition condition.
The status of steps transfers when all of the following conditions are met.
z
Step Transfer Condition
1 All transition conditions have been met.
2 All steps before the transition point are in the active status.
Note: The step transfers even if the connecting step after the transition is active.
Some steps do not have an action to execute. These steps will remain in the waiting
status, with no processing to perform until the transition conditions are met.
Steps, which do not have an action to execute, are referred to as “dummy steps”.
Step Types
There are following types of steps:
• Initial step
• Normal step
• Subchart step
Step 1
Step 1
Normal
Step
Initial
Step
Step 1
Subchart 1
Subchart
Step