Monitor Status Flags

The controller supports status keywords you can use in your logic to monitor specific events:
  • The status keywords are
    not c
    ase sensitive.
  • Because the status flags can change so quickly, the
    Logix Designer
     application does
    not
     display the status of the flags (that is, even when a status flag is set, an instruction that references that flag is not highlighted).
  • You
    cannot
    define a tag alias to a keyword.
You can use these keywords:
To determine if:
Use:
the value you are storing cannot fit into the destination because it is either:
  • greater than the maximum value for the destination, or
  • less than the minimum value for the destination
Important:
 Each time S:V goes from cleared to set, it generates a minor fault (type 4, code 4)
S:V
the instruction’s destination value is 0
S:Z
the instruction’s destination value is negative
S:N
an arithmetic operation causes a carry or borrow that tries to use bits that are outside of the data type
For example:
  • adding 3 + 9 causes a carry of 1
  • subtracting 25 - 18 causes a borrow of 10
S:C
this is the first, normal scan of the routines in the current program
S:FS
at least one minor fault has been generated:
  • The controller sets this bit when a minor fault occurs due to program execution.
  • The controller does not set this bit for minor faults that are not related to program execution, such as battery low.
S:MINOR
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