Structured Text; Bumpless Restart - Allen-Bradley Logix5000 Reference Manual

Structured Text

IF (Local:0:I.Ch0Fault) THEN
TIC101.SWM [:=] 1;
ELSE
TIC101.SWM := 0;
END_IF;
IF (Local:0:I.RollingTimestamp<>PreviousTimestamp) OR
(Local:0:I.Ch0Fault) THEN
PreviousTimestamp := Local:0:I.RollingTimestamp;
PID(TIC101,Local:0:I.Ch0Data,Local:0:I.Ch1Data,
Local:1:O.Ch0Data,0,Local:1:I.Ch0InHold,
Local:1:I.Ch0Data);
END_IF;

Bumpless Restart

The PID instruction can interact with the 1756 analog output modules to
support a bumpless restart when the controller changes from Program
to Run mode or when the controller powers up.
When a 1756 analog output module loses communications with the controller
or senses that the controller is in Program mode, the analog output module sets
its outputs to the fault condition values you specified when you configured the
module. When the controller then returns to Run mode or re-establishes
communications with the analog output module, you can have the PID
instruction automatically reset its control variable output equal to the analog
output by using the Inhold bit and Inhold Value parameters on the
PID instruction.
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Special Instructions (FBC, DDT, DTR, PID) Chapter 13
525