Allen-Bradley LOGIX 5000 User Manual

Process Control Instructions
Chapter 1
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018 25
Execution
Function Block
Condition/State Action Taken
Prescan Rung-condition-in bits are cleared to false.
Rung-condition-in is false Rung-condition-in bits are cleared to false.
Rung-condition-in is true Rung-condition-in bits are set to true.
The instruction executes.
Postscan Rung-condition-in bits are cleared to false.
Structured Text
Condition/State Action Taken
Prescan See Prescan in the Function Block table.
Normal Execution See Rung-condition-in is true in the Function Block table.
Postscan See Postscan in the Function Block table.
Example
The ALM instruction is typically used either with analog input modules (such as
1771 I/O modules) that do not support on-board alarming, or to generate alarms
on a calculated variable. In this example, an analog input from a 1771-IFE module
is first scaled to engineering units using the SCL instruction. The Out of the SCL
instruction is an input to the ALM instruction to determine whether to set an
alarm. The resulting alarm output parameters could then be used in your program
and/or viewed on an operator interface display.
Function Block
Structured Text
SCL_01.IN := Input0From1771IFE;

Allen-Bradley LOGIX 5000 Specifications

General

Brand	Allen-Bradley
Model	LOGIX 5000
Category	Controller
Language	English