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What is the FFB execution order on Unity Pro FBD section?

Published date: 19 November 2020

Some customers would like to know the execution order of FFB on Unity Pro FBD section, because sometimes they want that one FFB be executed before other. 

Product Line
Control Expert / Unity Pro all versions.

This resolution was created using Unity Pro v13.0 running on Windows 10 version 1703


The execution order is determined by the position of the FFBs in the section (executed from left to right and from top to bottom) and is displayed with execution numbers on the top right corner of the FFB. When your logic has FFB inputs that comes from another FFB, the execution order will be as bellow:
  1. Execute from top to bottom all FFBs that don't have another FFB as input (on the left side)
  2. Execute from top to bottom all FFBs that have another FFB as inpput
​The picture bellow shows the execution order and you can see that the FFB 13 will be executed before the 11 that is above.

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