Allen-Bradley LOGIX 5000

Process Control Instructions
Chapter 1
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018 135
Execution
Function Block
Condition/State Action Taken
Prescan EnableIn and EnableOut bits are cleared to false.
Tag.EnableIn is false EnableIn and EnableOut bits are cleared to false.
Tag.EnableIn is true EnableIn and EnableOut bits are set to true.
The instruction executes.
Instruction first run N/A
Instruction first scan HeatOut and CoolOut are cleared to false.
HeatTimePercent and CoolTimePercent are cleared to
0.0.
Postscan EnableIn and EnableOut bits are cleared to false.
Structured Text
Condition/State Action Taken
Prescan See Prescan in the Function Block table.
Normal Execution See Tag.EnableIn is true in the Function Block table.
Postscan See Postscan in the Function Block table.
Example
In this example, a PIDE instruction executes in a slow, lower priority task because
it is a slow, temperature loop. The output of the PIDE instruction is a controller-
scoped tag because it becomes the input to an SRTP instruction. The SRTP
instruction executes in a faster, higher priority task so that the pulse outputs are
more accurate