SFC parameters

In addition to the module-level parameters that all modules have, modules that contain SFC algorithms have additional module-level parameters. They are as follows:

• AUTO_ADVANCE - When TRUE, the SFC advances without user input in On-line and Debug views. When FALSE, the SFC is stopped and must be manually advanced.

• COMMAND - These are the commands that users can issue for the SFC. They are as follows:

  • Stop Sequence - Halts execution of the SFC.

  • Start Sequence - Starts an idle SFC or restarts a stopped SFC.

  • Reset Sequence - Sets a stopped SFC to the idle state.

• CONFIRM_FAIL - Activates confirmation of failing for the composite. The default is False. This is set whenever an action has a confirmed timeout before the expression used in confirming becomes True.

• ERROR - ERROR is a Boolean parameter whose value is True when an SFC Action has a run error or is unresolved. A run error occurs when the Action fails, for example, when an assignment is unsuccessful because a parameter cannot be written due to a function block being in the wrong mode. The Action is unresolved when any referenced parameter is unresolved in the Action expressions (action, delay, confirm, and confirm timeout expressions where applicable). 

• INITIAL_STATE - Defines the state that the SFC is in when downloaded (Sequence Active or Sequence Idle). The default is Sequence Active.

• RERROR - A Boolean parameter whose value is True when an SFC Action is resolved and a run error occurs. A run error occurs when the Action fails, for example, when an assignment is unsuccessful because a parameter cannot be written due to a function block being in the wrong mode. ERROR is always True when RERROR is True. The Action is resolved when all referenced parameters are resolved in the Action expressions (action, delay, confirm, and confirm timeout expressions where applicable). 

• STATE - Indicates the current state of the SFC. Possible states and their meanings are as follows:

  • Sequence Idle - The SFC has been reset.

  • Sequence Active - The SFC is running.

  • Sequence Stopped - The SFC has been stopped by a stop command.

  • Sequence Complete - The SFC has run to completion; no steps or transitions are active. (You must reset the SFC.)

  • Sequence Blocked - All active transitions are disabled.

• STATUS - Indicates the current status of the SFC. Possible statuses are as follows:

  • Okay - There are no errors.

  • Component Disabled - Indicates that steps, transitions, or actions might be disabled.

  • Component Error - An action or transition has detected an error.

  • Out of Service - n/a for SFC.

  • Breakpoint Set - n/a for SFC.

  • Debug View Active - A debug view is active and a user could currently be editing the downloaded module.

  • Value Forced - A user has set a parameter to a particular value during an Online View session. The module continues to run using this value until you remove the forced value.

  • Unresolved Reference - An action or transition references a parameter that cannot be resolved.

  • Not running - The module is not executing.

  • FBAbnormActive - a problem exists in one of the function blocks referenced in this SFC. That function block will have the ABNORM_ACTIVE parameter set to True.

• TIME - The amount of time the SFC has been running. This is the accumulated time that has passed since the sequence was started.

The following table lists additional parameters that SFC steps and transitions have.