Rockwell Automation Logix 5000 User Manual

Chapter 1 Program a Function Block Diagram
16 Rockwell Automation Publication 1756-PM009J-EN-P - March 2022
The order of execution is only relative to the blocks that are wired together.
The two groups of blocks in this example are not wired together. The blocks
within a specific group execute in the appropriate order in relation to the
blocks in that group.
To create a feedback loop around a block, wire an output pin of the block to an
input pin of the same block. In this example, the loop contains only a single
block, so execution order does not matter.
If a group of blocks are in a loop, the controller cannot determine which block
to execute first, and it cannot resolve the loop, as illustrated in this example.
To identify which block to execute first, mark the input wire that creates the
loop (the feedback wire) with the Assume Data Available indicator. In this
example, block 1 uses the output from block 3 that was produced in the
previous execution of the routine.
The Assume Data Available indicator defines the data flow within the loop.
The arrow indicates that the data serves as input to the first block in the loop.
Do not mark all the wires of a loop with the Assume Data Available indicator.
Resolve a loop

Rockwell Automation Logix 5000 Specifications

General

Brand	Rockwell Automation
Model	Logix 5000
Category	Controller
Language	English