SFC Execution at Runtime
Within a chart, all valid transitions are evaluated first, and then actions of active steps are performed. The chart is evaluated from the left to the right and from the top to the bottom. Below is an example:
Execution order: - Evaluate transitions: 1, 101, 2 - Manage steps: 1, 101, 201, 102 |
In case of a divergence, 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.
The initial steps define the initial status of the program when it is started. All top level (main) programs are started when the application starts. Child programs are explicitly started from action blocks within the parent programs.
The evaluation of transitions leads to changes of active steps, 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 (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
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Execution of SFC within the IEC"International Electrotechnical Commission" IEC is a not-for-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies 61131 target is sampled according to the target cycles. When a transition is crossed within a cycle, the following steps are activated, and the evaluation of the chart will continue on the next cycle. If several consecutive transitions are TRUE within a branch, only one of them is crossed within one target cycle.
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Some run-timeIn computer science, runtime (or run-time) describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time). Within KAS, runtime also refers to the virtual machine that manage the program written in a computer language while it is running systems can support exclusivity of the transitions within a ulergence or not. Please refer to OEM"Original equipment manufacturer" A term that refers to containment-based re-branding, namely where one company uses a component of another company within its product, or sells the product of another company under its own brand. OEM refers to the company that originally manufactured the product instructions for further information about SFC support.