Allen-Bradley LOGIX 5000 Reference Manual page 89

Process Control Instructions
The following diagram shows how the PIDE instruction changes between
Program control and Operator control.
(1) The instruction remains in Operator control mode when ProgOperReq is set.
Operating Modes
The PIDE instruction supports the following PID modes.
PID Operating Description
Mode
Cascade/Ratio While in Cascade/Ratio mode the instruction computes the change in CV. The instruction regulates CV to
maintain PV at either the SPCascade value or the SPCascade value multiplied by the Ratio value.
SPCascade comes from either the CVEU of a primary PID loop for cascade control or from the
"uncontrolled" flow of a ratio-controlled loop.
Select Cascade/Ratio mode using either OperCasRatReq or ProgCasRatReq:
Set OperCasRatReq to request Cascade/Ratio mode. Ignored when ProgOper, ProgOverrideReq,
ProgHandReq, OperAutoReq, or OperManualReq is set, or when AllowCasRat is cleared.
Set ProgCasRatReq to request Cascade/Ratio mode. Ignored when ProgOper or AllowCasRat is cleared or
when ProgOverrideReq, ProgHandReq, ProgAutoReq, or ProgManualReq is set.
Auto While in Auto mode the instruction computes the change in CV. The instruction regulates CV to
maintain PV at the SP value. If in program control, SP = SPProg; if in Operator control, SP = SPOper.
Select Auto mode using either OperAutoReq or ProgAutoReq:
Set OperAutoReq to request Auto mode. Ignored when ProgOper, ProgOverrideReq, ProgHandReq, or
OperManualReq is set.
Set ProgAutoReq to request Auto mode. Ignored when ProgOper is cleared or when ProgOverrideReq,
ProgHandReq, or ProgManualReq is set.
Manual While in Manual mode the instruction does not compute the change in CV. The value of CV is
determined by the control. If in Program control, CV = CVProg; if in Operator control, CV = CVOper.
Select Manual mode using either OperManualReq or ProgManualReq:
Set OperManualReq to request Manual mode. Ignored when ProgOper, ProgOverrideReq, or
ProgHandReq is set.
Set ProgManualReq to request Manual mode. Ignored when ProgOper is cleared or when
ProgOverrideReq or ProgHandReq is set.
Override While in Override mode the instruction does not compute the change in CV.
CV = CVOverride, regardless of the control mode. Override mode is typically used to set a "safe state" for
the PID loop.
Select Override mode using ProgOverrideReq:
Set ProgOverrideReq to request Override mode. Ignored when ProgHandReq is cleared.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Chapter 1
89