The following state transition diagram represents the phase logic either as a phase logic module or a phase in a unit module.
It executes the logic associated with each state of the phase. The phase logic, which runs in the controller, contains instructions on how to control each state of a phase of a recipe. You write the state logic with an SFC by creating steps and the transition logic to move from one step to another.
The five active states (Running, Holding, Aborting, Restarting and Stopping) contain user-defined logic that controls the phase.
During the passive states (Idle, Held, Complete, Stopped, Aborted), the phase waits for a new command.
The Failure_Monitor executes continuously and contains user logic to check for failure conditions. Detection of a failure condition automatically forces the phase from the Running state to the Holding state.
