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Statemachine

class Statemachine

Each controller has a state machine. It is generated automatically when the controller is created. The state machine describes the sequence or logic of a controller. The state machine is based on the specification of a UML state machine.

The statemachine has a graphical representation (diagram). This supports the developer when creating states and transitions.

The UML state diagram shows the different states a [controller] can be in and the transitions between these states. A state represents a stage in the behavior pattern of a controller. It is possible to have start and end states. An initial state, also called creation state, is the state in which a controller is at startup, while an end state is a state from which no transitions lead out. A transition is a transition from one state to another and is triggered by an event that is either internal or external to the controller.

Open the statemachine resource

Double-click on the statemachine property to get to the statemachine resource:

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Open the state machine diagram

There are several ways to get to the statemachine diagram:

  • Click on the aggregation symbol:

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  • From the context menu of the controller:

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  • Double-click the Controller Instance in Controller Tree

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Start Definition

First, a starting point must be defined. The starting point determines the state in which the control is started when the control is switched on.

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State types

There are different types of states:

State

class State extends StateBase

SuperState

class SuperState extends StateBase, AStatemachineStart, AJunctionProperty

SuperState_withBusyFinal

This state extends the SuperState with an initialization function. When this state is created, a start state, a transition state and a target state are created.

class SuperState_WithBusyFinal extends SuperState

Best practice

If possible, the SuperState_WithBusyFinal should be used instead of a simple state. This automatically creates an often required transition state.

Create a state

  • Selection of the state type from the palette:

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  • Creating a transition from start to first state (in this case the SuperState 'INIT_Group')

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Sequence behaviour of the state machine

The following section describes the behavior when changing states.

Situation 1: start → state

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sequenceDiagram
 loop every PLC task cycle
    task->>STATE1_entry: ev_entry
  activate task
   activate STATE1_entry
    STATE1_entry->>STATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task


  task->>STATE1_state: ev_cyclic
  activate task
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no tranistion active
   deactivate STATE1_state
  deactivate task
 end

Situation 2: start →  state → transition (self) → state

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sequenceDiagram
 loop every PLC task cycle
     task->>STATE1_entry: ev_entry
  activate task
   activate STATE1_entry
    STATE1_entry->>STATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: transition_1==true
   deactivate STATE1_state
  deactivate task


  task->>STATE1_exit: ev_exit [transition_1==true]
  activate task
   activate STATE1_exit  
    STATE1_exit->>TRANSITION_1_function: ev_transition [transition_1==true]
   deactivate STATE1_exit 
   activate TRANSITION_1_function
    TRANSITION_1_function->>STATE1_entry: ev_entry [transition_1==true]
   deactivate TRANSITION_1_function
   activate STATE1_entry
    STATE1_entry->>STATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no tranistion active
   deactivate STATE1_state
  deactivate task

  task->>STATE1_state: ev_cyclic
  activate task
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no tranistion active
   deactivate STATE1_state
  deactivate task
 end

Situation 3: start →  state → transition → state

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sequenceDiagram
 loop every PLC task cycle
     task->>SSTATE1_entry: ev_entry
  activate task
   activate SSTATE1_entry
    SSTATE1_entry->>STATE1_entry: ev_entry
   deactivate SSTATE1_entry
   activate STATE1_entry
    STATE1_entry->>SSTATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task

  task->>SSTATE1_state: ev_cyclic
  activate task
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task
 end

Situation 4: start →  super state → state

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sequenceDiagram
 loop every PLC task cycle
     task->>SSTATE1_entry: ev_entry
  activate task
   activate SSTATE1_entry
    SSTATE1_entry->>STATE1_entry: ev_entry
   deactivate SSTATE1_entry
   activate STATE1_entry
    STATE1_entry->>SSTATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task

  task->>SSTATE1_state: ev_cyclic
  activate task
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task
 end

To be considered:

The cyclic part of the superstates is only executed for the first time after the completed 'entry' cycle.

Situation 4: start →  super state → state → super state → state

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No transition active

sequenceDiagram
 loop every PLC task cycle
     task->>SSTATE1_entry: ev_entry
  activate task
   activate SSTATE1_entry
    SSTATE1_entry->>STATE1_entry: ev_entry
   deactivate SSTATE1_entry
   activate STATE1_entry
    STATE1_entry->>SSTATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task

  task->>SSTATE1_state: ev_cyclic
  activate task
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: no transition active
   deactivate STATE1_state
  deactivate task
 end

Transition_1 active

sequenceDiagram
 loop every PLC task cycle
     task->>SSTATE1_entry: ev_entry
  activate task
   activate SSTATE1_entry
    SSTATE1_entry->>STATE1_entry: ev_entry
   deactivate SSTATE1_entry
   activate STATE1_entry
    STATE1_entry->>SSTATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>task: transition_1 active
   deactivate SSTATE1_state
  deactivate task

  task->>STATE1_exit: ev_exit [transition_1==true]
  activate task
   activate STATE1_exit
    STATE1_exit->>SSTATE1_exit: ev_exit [transition_1==true]
   deactivate STATE1_exit
   activate SSTATE1_exit
    SSTATE1_exit->>TRANSITION_1_function: ev_transition [transition_1==true]
   deactivate SSTATE1_exit
   activate TRANSITION_1_function
    TRANSITION_1_function->>SSTATE2_entry: ev_transition [transition_1==true]
   deactivate TRANSITION_1_function
   activate SSTATE2_entry
    SSTATE2_entry->>STATE2_entry: ev_transition [transition_1==true]
   deactivate SSTATE2_entry
   activate STATE2_entry
    STATE2_entry->>SSTATE2_state: ev_cyclic
   deactivate STATE2_entry
   activate SSTATE2_state
    SSTATE2_state->>STATE2_state: ev_cyclic
   deactivate SSTATE2_state
   activate STATE2_state
    STATE2_state->>STATE2_state: check transition
    STATE2_state->>task: no transition active
   deactivate STATE2_state
  deactivate task

  task->>SSTATE2_state: ev_cyclic
  activate task
   activate SSTATE2_state
    SSTATE2_state->>SSTATE2_state: check transition
    SSTATE2_state->>STATE2_state: ev_cyclic
   deactivate SSTATE2_state
   activate STATE2_state
    STATE2_state->>STATE2_state: check transition
    STATE2_state->>task: no transition active
   deactivate STATE2_state
  deactivate task
 end

Transition_2 active

sequenceDiagram
 loop every PLC task cycle
     task->>SSTATE1_entry: ev_entry
  activate task
   activate SSTATE1_entry
    SSTATE1_entry->>STATE1_entry: ev_entry
   deactivate SSTATE1_entry
   activate STATE1_entry
    STATE1_entry->>SSTATE1_state: ev_cyclic
   deactivate STATE1_entry
   activate SSTATE1_state
    SSTATE1_state->>SSTATE1_state: check transition
    SSTATE1_state->>STATE1_state: ev_cyclic
   deactivate SSTATE1_state
   activate STATE1_state
    STATE1_state->>STATE1_state: check transition
    STATE1_state->>task: transition_2 active
   deactivate STATE1_state
  deactivate task

  task->>STATE1_exit: ev_exit [transition_2==true]
  activate task
   activate STATE1_exit
    STATE1_exit->>SSTATE1_exit: ev_exit [transition_2==true]
   deactivate STATE1_exit
   activate SSTATE1_exit
    SSTATE1_exit->>TRANSITION_2_function: ev_transition [transition_2==true]
   deactivate SSTATE1_exit
   activate TRANSITION_2_function
    TRANSITION_2_function->>SSTATE2_entry: ev_transition [transition_2==true]
   deactivate TRANSITION_2_function
   activate SSTATE2_entry
    SSTATE2_entry->>STATE2_entry: ev_transition [transition_2==true]
   deactivate SSTATE2_entry
   activate STATE2_entry
    STATE2_entry->>SSTATE2_state: ev_cyclic
   deactivate STATE2_entry
   activate SSTATE2_state
    SSTATE2_state->>STATE2_state: ev_cyclic
   deactivate SSTATE2_state
   activate STATE2_state
    STATE2_state->>STATE2_state: check transition
    STATE2_state->>task: no transition active
   deactivate STATE2_state
  deactivate task

  task->>SSTATE2_state: ev_cyclic
  activate task
   activate SSTATE2_state
    SSTATE2_state->>SSTATE2_state: check transition
    SSTATE2_state->>STATE2_state: ev_cyclic
   deactivate SSTATE2_state
   activate STATE2_state
    STATE2_state->>STATE2_state: check transition
    STATE2_state->>task: no transition active
   deactivate STATE2_state
  deactivate task
 end