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What is the behavior of the EFB EN and ENO pins ?

Title
 Behavior of the EFB EN and ENO pins
 
Issue
 Behavior of the EFB EN and ENO pins
 
Product Line
M340, M580 , Quantum
 
Environment
Unity Pro
 
Cause
N/A
 
Resolution
The behavior of the EFB EN and ENO pins, from Unity help, explains that for function blocks a user can also enable an additional Boolean EN (Enable) input or ENO (Enable Out) output, or both.
When these variables are used, the execution of the operations defined by the function block shall be controlled according to the following rules:
1.  If the value of EN is FALSE (0) when the function block instance is invoked, the assignments of actual values to the function block inputs may or may not be made in an implementation-dependent fashion, the operations defined by the function block body shall not be executed and the value of ENO shall be reset to FALSE (0) by the programmable controller system.

2.  Otherwise, the value of ENO shall be set to TRUE (1) by the programmable controller system, the assignments of actual values to the function block inputs shall be made and the operations defined by the function block body shall be executed. These operations can include the assignment of a Boolean value to ENO.

3.  If the ENO output is evaluated to FALSE (0), the values of the function block outputs (VAR_OUTPUT) keep their states from the previous invocation.
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