Manual

Publication LOGIX-UM001B-EN-P - April 2010 77
Equipment Phase Instructions (PSC, PCMD, POVR, PFL, PCLF, PXRQ, PRNP, PPD, PATT, PDET) Appendix A
Execution:
Example:
Relay Ladder
Structured Text
(*If Drain_Tank_Restart = on, then:
Clear the failure code for the Drain_Tank
equipment phase.
Restart the Drain_Tank equipment phase.
Turn off Drain_Tank_Restart.*)
If Drain_Tank_Restart Then
PCLF(Drain_Tank);
PCMD(Drain_Tank,Restart,0);
Drain_Tank_Restart := 0;
End_If;
Condition Relay Ladder Action Structured Text Action
prescan The rung-condition-out is set to false. No action taken.
rung-condition-in is false The rung-condition-out is set to false. N/A
rung-condition-in is true • The instruction executes.
• The rung-condition-out is set to true.
N/A
scan of structured text N/A In structured text, instructions execute each time
they are scanned. To limit the scan of an instruction,
use a qualifier of an SFC action and/or a structured
text construct.
instruction execution The instruction clears the value of the failure code
for the specified equipment phase.
The instruction clears the value of the failure code
for the specified equipment phase.
postscan The rung-condition-out is set to false. No action taken.
If Drain_Tank_Restart = 1 (restart the Drain_Tank equipment phase) then
Clear the failure code of the Drain_Tank equipment phase
Change the state of the Drain_Tank equipment phase to restarting via the restart command.
Drain_Tank_Restart =0.