Process Control Instructions
76 Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
SP REAL Current setpoint value. The value of SP is used to control CV when in Auto or
Cascade/ Ratio mode.
SPPercent REAL The value of SP expressed in percent of span of PV.
SPPercent = ((SP - PVEUMin) x 100) / PVSpan
PV Span calculation: PVSpan = (PVEUMax - PVEUMin)
SPHAlarm BOOL SP high alarm indicator.
Set to true when the SP > SPHLimit.
SPLAlarm BOOL SP low alarm indicator.
Set to true when the SP < SPLLimit.
PVPercent REAL PV expressed in percent of span.
PVPercent = ((PV- PVEUMin) x 100) / PVSpan
PV Span calculation: PVSpan = (PVEUMax - PVEUMin)
E REAL Process error. Difference between SP and PV, scaled in PV units.
EPercent REAL The error expressed as a percent of span.
InitPrimary BOOL Initialize primary loop command. Set to true when not in Cascade/Ratio mode
or when CVInitializing is true. This signal is normally used by the CVInitReq
input of a primary PID loop.
WindupHOut BOOL Windup high indicator. Set to true when CV high or CV low limit (depending on
the control action) or SP high limit has been reached. This signal is typically
used by the WindupHIn input to prevent the windup of the CV output on a
primary loop.
WindupLOut BOOL Windup low indicator. Set to true when CV high or CV low limit (depending on
the control action) or SP low limit has been reached. This signal is typically used
by the WindupLIn input to prevent the windup of the CV output on a primary
loop.
Ratio REAL Current ratio multiplier.
RatioHAlarm BOOL Ratio high alarm indicator. Set to true when Ratio > RatioHLimit.
RatioLAlarm BOOL Ratio low alarm indicator. Set to true when Ratio < RatioLLimit.
ZCDeadbandOn BOOL Zero crossing deadband indicator. When true the value of CV does not change. If
ZCOff is true, then ZCDeadbandOn is set to true when | E | is within the
ZCDeadband range. If ZCOff is false, then ZCDeadbandOn is set to true when | E |
crosses zero and remains within the ZCDeadband range. ZCDeadbandOn is
cleared to false when | E | exceeds the deadband range or when ZCDeadband =
0.
PVHHAlarm BOOL PV high-high alarm indicator. Set to true when PV PVHHLimit. Cleared to
false when PV < (PVHHLimit - PVDeadband)
PVHAlarm BOOL PV high alarm indicator. Set to true when PV PVHLimit. Cleared to false
when PV < (PVHLimit - PVDeadband)
PVLAlarm BOOL PV low alarm indicator. Set to true when PV PVLLimit. Cleared to false
when PV > (PVLLimit + PVDeadband)
PVLLAlarm BOOL PV low-low alarm indicator. Set to true when PV PVLLLimit. Cleared to
false when PV > (PVLLLimit + PVDeadband)
PVROCPosAlarm BOOL PV positive rate-of-change alarm indicator. Set to true when calculated PV rate-
of-change PVROCPosLimit.
PVROCNegAlarm BOOL PV negative rate-of-change alarm indicator. Set to true when calculated PV
rate-of-change (PVROCNegLimit x -1).
DevHHAlarm BOOL Deviation high-high alarm indicator. Set to true when
PV (SP + DevHHLimit). Cleared to false when
PV < (SP + DevHHLimit - DevDeadband)
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