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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 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

When the same step is linked before and after the transition, it remains active (no pulse in its activity signal)

Divergences

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:

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

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