Structured Text; Pid Structure - Allen-Bradley Logix5000 Reference Manual

Chapter 13 Special Instructions (FBC, DDT, DTR, PID)
PID(PID,ProcessVariable,
Tieback,ControlVariable,
PIDMasterLoop,InholdBit,
InHoldValue);
Mnemonic: Data Type
.CTL DINT
.SP REAL
.KP REAL
.KI REAL
.KD REAL
512

Structured Text

The operands are the same as those for the relay ladder PID instruction.
However, you specify the Setpoint, Process Variable, and Output percent by
accessing the .SP, .PV.and .OUT members of the PID structure, rather than by
including values in the operand list.

PID Structure

Description
The .CTL member provides access to the status members (bits) in one, 32-bit word. The PID instruction sets
bits 07...15.
This bit Is this member
31 .EN
30 .CT
29 .CL
28 .PVT
27 .DOE
26 .SWM
25 .CA
24 .MO
23 .PE
22 .NDF
21 .NOBC
20 .NOZC
This bit Is this member, which the PID instruction sets
15 .INI
14 .SPOR
13 . OLL
12 .OLH
11 .EWD
10 .DVNA
09 .DVPA
08 .PVLA
07 .PVHA
Setpoint
Independent Proportional gain (unitless)
Dependent Controller gain (unitless)
Independent Integral gain (1/sec)
Dependent Reset time (minutes per repeat)
Independent Derivative gain (seconds)
Dependent Rate time (minutes)
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011