The ProgramStateMachineType components consist of a set of References to the Object instances of StateTypes, TransitionTypes, EventTypes and the Methods that collectively define the Program FiniteStateMachine.

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Figure 5 – Program References

Figure 5 illustrates the component References that define the associations between two of the ProgramStateMachineType’s states, Ready and Running. The complementary ReferenceTypes have been omitted to simplify the illustration.

Table 6 specifies the ProgramStateMachineType’s state Objects. These Objects are instances of the StateType defined in OPC 10000-5, Annex B. Each state is assigned a unique StateNumber value. Subtypes of the ProgramStateMachineType can add references from any state to a subordinate or nested StateMachine Object to extend the FiniteStateMachine.

Table 6 – Program states

BrowseName

References

Target BrowseName

Value

Target TypeDefinition

NOTES

States

Halted

HasProperty

StateNumber

11

PropertyType

ToTransition

HaltedToReady

TransitionType

FromTransition

RunningToHalted

TransitionType

FromTransition

SuspendedToHalted

TransitionType

FromTransition

ReadyToHalted

TransitionType

Ready

HasProperty

StateNumber

12

PropertyType

FromTransition

HaltedToReady

TransitionType

ToTransition

ReadyToRunning

TransitionType

FromTransition

RunningToReady

TransitionType

ToTransition

ReadyToHalted

TransitionType

Running

HasProperty

StateNumber

13

PropertyType

ToTransition

RunningToHalted

TransitionType

ToTransition

RunningToReady

TransitionType

ToTransition

RunningToSuspended

TransitionType

FromTransition

ReadyToRunning

TransitionType

FromTransition

SuspendedToRunning

TransitionType

Suspended

HasProperty

StateNumber

14

PropertyType

ToTransition

SuspendedToRunning

TransitionType

ToTransition

SuspendedToHalted

TransitionType

ToTransition

SuspendedToReady

TransitionType

FromTransition

RunningToSuspended

TransitionType

The Halted state is the idle state for a Program. It can be an initial state or a terminal state. As an initial state, the Program Invocation cannot begin execution due to conditions at the Server. As a terminal state, Halted can indicate either a failed or completed Program. A subordinate state or result can be used to distinguish the nature of the termination. The Halted state references four Transition Objects, which identify the allowed state transitions to the Ready state and from the Ready, Running, and Suspended states.

The Ready state indicates that the Program is prepared to begin execution. Programs that are ready to begin upon their creation may transition immediately to the Ready state. The Ready state references four Transition Objects, which identify the allowed state transitions to the Running and Halted states and from the Halted and Ready states.

The Running state indicates that the Program is actively performing its Function. The Running state references five Transition Objects, which identify the allowed state transitions to the Halted, Ready, and Suspended states and from the Ready and Suspended states.

The Suspended state indicates that the Program has stopped performing its Function, but retains the ability to resume the Function at the point at which it was executing when suspended. The Suspended state references four Transition Objects, which identify the allowed state transitions to the Ready, Running, and Halted state and from the Ready state.

ProgramStateMachineType Transitions are instances of the TransitionType defined in OPC 10000-5 which also includes the definitions of the ToState, FromState, HasCause, and HasEffect references used. Table 7 specifies the transitions defined for the ProgramStateMachineType. Each transition is assigned a unique TransitionNumber. The Notes column indicates when a cause is referencing Methods and when effects are optional.

Table 7 – Program transitions

BrowseName

References

Target BrowseName

Value

Target TypeDefinition

Notes

Transitions

HaltedToReady

HasProperty

TransitionNumber

1

PropertyType

ToState

Ready

StateType

FromState

Halted

StateType

HasCause

Reset

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

ReadyToRunning

HasProperty

TransitionNumber

2

PropertyType

ToState

Running

StateType

FromState

Ready

StateType

HasCause

Start

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

RunningToHalted

HasProperty

TransitionNumber

3

PropertyType

ToState

Halted

StateType

FromState

Running

StateType

HasCause

Halt

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

RunningToReady

HasProperty

TransitionNumber

4

PropertyType

ToState

Ready

StateType

FromState

Runnning

StateType

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

RunningToSuspended

HasProperty

TransitionNumber

5

PropertyType

ToState

Running

StateType

FromState

Suspended

StateType

HasCause

Suspend

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

SuspendedToRunning

HasProperty

TransitionNumber

6

PropertyType

ToState

Running

StateType

FromState

Suspended

StateType

HasCause

Resume

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

SuspendedToHalted

HasProperty

TransitionNumber

7

PropertyType

ToState

Halted

StateType

FromState

Suspended

StateType

HasCause

Halt

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

SuspendedToReady

HasProperty

TransitionNumber

8

PropertyType

ToState

Ready

StateType

FromState

Suspended

StateType

HasCause

Reset

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

ReadyToHalted

HasProperty

TransitionNumber

9

PropertyType

ToState

Halted

StateType

FromState

Ready

StateType

HasCause

Halt

Method

HasEffect

ProgramTransitionEventType

HasEffect

AuditProgramTransitionEventType

The HaltedToReady transition specifies the transition from the Halted to Ready states. It may be caused by the Reset Method.

The ReadyToRunning transition specifies the transition from the Ready to Running states. It is caused by the Start Method.

The RunningToHalted transition specifies the transition from the Running to Halted states. It is caused by the Halt Method.

The RunningToReady transition specifies the transition from the Running to Ready states. The RunningToSuspended transition specifies the Transition from the Running to Suspended states. It is caused by the Suspend Method.

The SuspendedToRunning transition specifies the transition from the Suspended to Running states. It is caused by the Resume Method.

The SuspendedToHalted transition specifies the transition from the Suspended to Halted states. It is caused by the Halt Method.

The SuspendedToReady transition specifies the transition from the Suspended to Ready states. It is caused internally.

The ReadyToHalted transition specifies the transition from the Ready to Halted states. It is caused by the Halt Method.

Two HasEffect references are specified for each Program transition. These effects are Events of ProgramTransitionEventType and AuditProgramTransitionEventType defined in 5.2.5. The ProgramTransitionEventType notifies Clients of the Program transition and conveys result data. The AuditProgramTransitionEventType is used to audit transitions that result from Program Control Methods. The “Audit Server FacetProfile defined in OPC 10000-7 requires support of the AuditProgramTransitionEventType.

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Figure 6 – ProgramStateMachineType causes and effects