Omron SYSMAC CX-Programmer 8.1, Operation Manual

Page: 66 / 154

Elements of SFC Section 2-3
50
Flags Used to Monitor a Step’s Active Status
Step Flags
These flags indicate the steps active/inactive status.
The flags are expressed as
Step_name.X , and each flag will be ON when the
corresponding step is active or OFF when the corresponding step is inactive.
Step Timers
These timers indicate how long each step has been active.
The timers are expressed as
StepName.T , and the timer’s units can be set to 100 ms
or 1 s units for each step.
Procedures:
Adding a Step
Right-click a transition, and select Add Step .
Defining the Initial Step
To convert a normal step to an initial step, right-click the normal step, and select Step
Type - Initial .
Adding a Subchart Step
Right-click a transition, and select Add Subchart Step - New Subchart .
Defining a Subchart
Right-click a Subcharts folder in the project workspace, and select Insert SFC
Subchart .
Administering a Step Control Instruction
Input the instruction as a regular ladder instruction, and specify the target step flag.
2-3-2 Transitions
A transition represents the condition in which the active status transfers from the step
before the transition to the step after it. One transition must be set between steps.
The transition is represented as shown below.
Trans1
FALSE
Operation of Transitions
When the transition condition is met, the step before the transition becomes inactive
and the step after it becomes active.
In this way, the transition controls the program flow from step to step.
• When representing transition conditions with transition programs, turning a transition
program name ON will turn the represented transition condition ON.
Transition Conditions
Transition conditions are to be defined on the right-hand side of the figure.
When a transition is added to the SFC editor, its default condition is the ST expression
“FALSE”.
The condition equation for a transition can be set to any one of the following:
•
Bit (Boolean variable or actual address)
•
ST expression
•
Transition program name