512 Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Chapter 13 Special Instructions (FBC, DDT, DTR, PID)
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
PID(PID,ProcessVariable,
Tieback,ControlVariable,
PIDMasterLoop,InholdBit,
InHoldValue);
Mnemonic: Data Type Description
.CTL DINT 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
.SP REAL Setpoint
.KP REAL Independent Proportional gain (unitless)
Dependent Controller gain (unitless)
.KI REAL Independent Integral gain (1/sec)
Dependent Reset time (minutes per repeat)
.KD REAL Independent Derivative gain (seconds)
Dependent Rate time (minutes)
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