Rockwell Automation 1794-Lxxxx PhaseManager - Manual (Page 73)

Publication LOGIX-UM001B-EN-P - April 2010 73
Equipment Phase Instructions (PSC, PCMD, POVR, PFL, PCLF, PXRQ, PRNP, PPD, PATT, PDET) Appendix A
Guidelines for Using the PFL Instruction
Guideline Details
Put the PFL instruction in the
equipment phase. The PFL instruction sets the failure code for the equipment phase in which you put the
instruction. There is no operand to identify a specific equipment phase.
Typically, put the PFL instruction in a prestate routine for the equipment phase.
• The controller always scans the prestate routine, even when an equipment phase is in the
idle state.
• The controller scans the prestate routine before each scan of a state.
• Use the prestate routine to continuously monitor the health of an equipment phase as you
progress through its states.
Prioritize your failure codes. The PFL instruction sets the failure code only to a value greater than its current value.
• For example, if a PFL instruction sets the failure code = 102, another PFL instruction can
only set the failure code > 102.
• Make sure that you assign higher values to exceptions that require higher priority in their
handling. Otherwise, a lower priority exception may overwrite a more critical exception.
To take action when a failure occurs,
monitor the Failure member of the
PHASE tag. The PFL instruction writes its value to the Failure member of the PHASE tag for the equipment
phase.
current state
routine
prestate routine
When you create an equipment phase,
RSLogix 5000 software creates a tag for the
status of the equipment phase.
controller scope
name = phase_name
PHASE data type
The PFL instruction writes its value to the
failure member for the equipment phase.