SFC parallel branches
"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 charts to represent parallel
operations. Parallel branches occur when more than several steps are connected
after the same transition. Parallel branches are drawn as double horizontal
lines:
When the transition before the divergence (1 on this example) is crossed, all steps beginning the parallel branches (101 and 201 here) are activated.
Sequencing of parallel branches can take different timing according to each branch execution.
The transition after the convergence (2 on this example) is crossed when all the steps connected before the convergence line (last step of each branch) are active. The transition indicates a synchronization of all parallel branches.
If needed, a branch can be finished with an "empty" step (with no action). It represents the state where the branch "waits" for the other ones to be completed.
You must take care of the following rules when drawing parallel lines in order to avoid dead locks in the execution of the program:
- All branches must be connected to the divergence and the convergence.
- An element of a branch must not be connected to an element outside the divergence.
How to create parallel branches?
To create double bars for a parallel branch you have to highlight a horizontal line and click the Spacebar to switch back and forth between single and double lines.
