Each sequential function chart can be configured to use one of the following Execution Modes:
This chart can be started via scripting or another chart's enclosing step on-demand. Any number of instances of this chart can be simultaneously running.
This chart can be started by the Gateway upon startup. It can not be executed in any other way. It is probable that this chart be designed to never end, the idea being that there will always be exactly one instance of this chart running.
This chart is not available for execution.
Steps are the parts of the chart that do useful work. Steps are represented as a rectangle that occupies a one-cell region of the chart, except for the begin and end steps, which are triangles. Steps might run scripts, or execute other charts depending on how you set them up.
There are four types of steps:
- Begin and End Steps
- Action Step
- Assertion Step
- Enclosing Step
In addition to these, there are multiple SFC elements that allow for more complex logic in your SFC.
Each chart you define in the Designer may be invoked multiple times, and each invocation will start a new instance of that chart. The instances may be started with different starting parameters which affect how the chart works. Each instance runs completely independently of the other instances. The ability to have multiple instances of a chart is one important feature that makes SFCs within Ignition different than SFCs inside of PLCs.
For information about the scripting API methods available for sequential function charts, see System Functions.