Troubleshoot Sequencing Parameters

Troubleshoot Sequencing Parameters

The following table explains the types of sequencing parameter issues with possible causes.
Problem
Possible causes
A sequencing output parameter with a configured expression does not appear to evaluate.
  • Verify the sequence output parameter has a valid configured expression.
  • Verify the sequence program has become COMPLETE, STOPPED, or ABORTED. Entering one of these states triggers the
    Equipment Sequence
     to automatically evaluate the expressions of its sequencing output parameters.
The Valid attribute of sequencing output parameters is set FALSE.
  • The sequence output parameter's InitializeAsValid flag is configured to be FALSE. Any time the sequence is initialized, the Valid flag of these tags is assigned the value of the InitializeAsValid flag.
  • The expression of these tags references a sequencing parameter or step tag that has its Valid flag set FALSE. When a parameter expression evaluates, the
    Value
     is assigned the result of the mathematical operation. The
    Valid
    value is then assigned the result of applying the logical AND operation to all terms having a
    Valid
    flag (terms of SEQ_<type> data type). If any term has its Valid attribute set FALSE, the sequencing output parameter's Valid attribute is set FALSE.
  • The expression on a sequencing output parameter has not evaluated yet, so the
    Value
    attribute's value
    remains its initialized value.
  • The Valid attribute of sequencing outputs is not set when the tag’s Value is updated in these ways:
    • The value is updated as a result of a configure Connection.
    • The value is updated as a result of executing an instruction.
Sequencing output parameters values appear to be valid when they should not be valid.
  • Check the configuration of the InitializeAsValid attribute. They may be initialized as Valid.
  • A control engineer or operator may have assigned a value to the sequence output parameter, with a
    Usage
    of read-write, which sets the Valid flag TRUE.
  • The control engineer or operator may have commanded the sequence output parameter to evaluate, which could set the Valid flag TRUE (all terms of SEQ_<type> data type would have to have their Valid flags set TRUE).
Provide Feedback
Have questions or feedback about this documentation? Please submit your feedback here.