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Rockwell Automation Publication 2080-UM002N-EN-E - November 2022
Appendix E PID Function Blocks
PID Function Block
This function block diagram shows the arguments in the PID function block.
The following table explains the arguments used in this function block.
Table 83 - PID Arguments
Parameter
Parameter
Type
Data Type
Description
Enable
Input
BOOL
Enable instruction.
TRUE = Start execution with current input parameters.
FALSE = CV equals zero.
PV
Input
REAL
Process Value. This value is typically read from an analog
input module.
The SI unit must be the same as Setpoint.
SP
Input
REAL
The set point value for the process.
AutoManual
Input
BOOL
Auto or manual mode selection:
TRUE = Normal operation of PID.
FALSE = Manual operation using CVManual.
CVManual
Input
REAL
Control value input defined for manual mode operation. The
valid range for CVManual is:
CVMin < CVManual < CVMax
CVMin
Input
REAL
Control value minimum limit.
If CV < CVMin, then CV = CVMin.
If CVMin > CVMax, and error occurs.
CVMax
Input
REAL
Control value maximum limit.
If CV > CVMax, then CV = CVMax.
If CVMax < CVMin, an error occurs.
Gains
Input
PID_GAINS
Gains of PID for controller.
Use the PID_GAINS data type to configure the Gains
parameter.
Control
Input
BOOL
Control direction of the process:
TRUE = Direct acting, such as Cooling.
FALSE = Reverse acting, such as Heating.
Llnit
Input
BOOL
Reserved for future use.
Active
Output
BOOL
Status of the PID controller:
TRUE = PID state is running.
FALSE = PID state is stopped.
CV
Output
REAL
The control value output.
If any error occurred, CV is 0.
AbsoluteError
Output
REAL
Absolute error is the difference between process value (PV)
and setpoint (SV) value.
Error
Output
BOOL
Indicates the existence of an error condition.
TRUE = PID has an error.
FALSE = PID has no errors.
ErrorID
Output
USINT
A unique numeric that identifies the error. The errors are
defined in PID error codes.
PID
PID
PV
Active
CV
AbsoluteError
SP
AutoManual
CVManual
CVMax
CVMin
Gains
Control
Error
Error ID
Llnit
Enable