SFC Transitions
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To change the number of a step, transition or jump, select it and hit Ctrl+ENTER keys.
The transition is marked by a small horizontal line that crosses a link drawn between the two steps.
The default direction for vertical links is from the top to the bottom
- Each transition is identified by a unique number in the SFC
"Sequential function chart"
It can be used to program processes that can be split into steps.
The main components of SFC are:
- Steps with associated actions
- Transitions with associated logic conditions
- Directed links between steps and transitions program. - Each transition must be completed with a Boolean condition that indicates if the transition can be crossed. The condition is a BOOL expression. If no condition is entered, it is assumed as always TRUE.
- In order to simplify the chart and reduce the number of drawn links, you can specify the activity flag of a step (GSnnn.X) in the condition of the transition.
Transitions define the dynamic behavior of the SFC chart, according to the following rules:
- A transition in crossed if:
- its condition is TRUE
- and if all steps linked to the top of the transition (i.e. before) are active
- When a transition is crossed:
- all steps linked to the top of the transition (i.e. before) are deactivated
- all steps linked to the bottom of the transition (i.e. after) are activated
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When the same step is linked before and after the transition, it remains active (no pulse in its activity signal)
It is possible to link a step to several transitions and thus create a divergence. The divergence is represented by a horizontal line. Transitions after the divergence represent several possible changes in the situation of the program.
All conditions are considered as exclusive, according to a "left to right" priority order. It means that a transition is considered as FALSE if at least one of the transitions connected to the same divergence on its left side is TRUE.
Below is an example:
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Transition 2 is crossed if: |
