Allen-Bradley LOGIX 5000 Reference Manual page 23

Process Control Instructions
Output Parameter
EnableOut
HHAlarm
HAlarm
LAlarm
LLAlarm
ROCPosAlarm
ROCNegAlarm
ROC
Status
InstructFault (Status.0)
DeadbandInv (Status.1)
ROCPosLimitInv (Status.2)
ROCNegLimitInv (Status.3)
ROCPeriodInv (Status.4)
Description
The ALM instruction provides alarm indicators for high-high, high, low, low-low,
rate-of-change positive, and rate-of-change negative. An alarm deadband is
available for the high-high to low-low alarms. A user-defined period for
performing rate-of-change alarming is also available.
High-high to Low-low Alarm
The high-high and low-low alarm algorithms compare the input to the alarm limit
and the alarm limit plus or minus the deadband.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Data Type Description
BOOL Indicates if instruction is enabled. Cleared to false if ROC
overflows.
BOOL The high-high alarm indicator.
Default = false
BOOL The high alarm indicator.
Default = false
BOOL The low alarm indicator.
Default = false
BOOL The low-low alarm indicator.
Default = false
BOOL The rate-of-change positive alarm indicator.
Default = false
BOOL The rate-of-change negative alarm indicator.
Default = false
REAL The rate-of-change output.
DINT Status of the function block.
BOOL The instruction detected one of the following execution errors.
This is not a minor or major controller error. Check the remaining
status bits to determine what occurred.
BOOL Invalid Deadband value.
BOOL Invalid ROCPosLimit value.
BOOL Invalid ROCNegLimit value.
BOOL Invalid ROCPeriod value.
Chapter 1
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