SFC Transitions

Transitions represent a condition that changes the program activity from a step to another.


  • To change the number of a step, transition, or jump, select it and press Ctrl+ENTER.

The transition is marked by a small horizontal line that crosses a link drawn between the two steps.

  • Each transition is identified by a unique number in the SFC 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.
  • To simplify the chart and reduce the number of drawn links, 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 these rules:

  • A transition is crossed if:
    • Its condition is TRUE and all steps linked to the top of the transition (before) are active.
  • When a transition is crossed:
    • All steps linked to the top of the transition (before) are deactivated.
    • All steps linked to the bottom of the transition (after) are activated.

Divergences

It is possible to link a step to several transitions and 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 a transition is considered as FALSE if at least one of the transitions connected to the same divergence on its left side is TRUE.

Example

Transition 1 is crossed if:

  • Step 1 is active and Cond1 is TRUE.

Transition 2 is crossed if:

  • Step 1 is active
    and Cond2 is TRUE
    and Cond1 is FALSE