The lowest level of procedural element in the procedural control model.
The smallest element of procedural control that can accomplish a process-oriented task is a phase. A phase may be subdivided into smaller parts. The steps and transitions as described in IEC 848: 1988 document one method of defining subdivisions of a phase.
A phase can issue one or more commands or cause one or more actions, such as
The execution of a phase may result in
The intent of the phase is to cause or define a process oriented action, while the logic or set of steps that make up a phase are equipment specific. Examples of phases include the following:
You can use SFC diagrams for phases.