Explanation of why the output of a Unity Pro instruction will be zero after the EN input of the block goes low.

Goals and Symptoms

When the EN input of a function block goes low Unity is designed to zero-out the outputs of blocks where links are attached, or maintain the last value if a variable is attached. Former users of Concept will be accustomed to the outputs remaining at their last state irrespective of whether a link or a variable is attached to the output.

NOTE: There is a a Project Setting in Unity which will maintain the output state of an EF when EN goes low. By default this setting is not selected.
To maintain the output state of a disabled EF go to Tools/Project Settings/Program/Language Common. Select "Maintain Output Links on Disabled EF or EN=0"
Selecting this option will negate the manner of operation described in this FAQ.

Causes and Fixes

In the image below an ADD_INT block is being fed by a link in one example and a variable in another with the EN input high.



When the EN input drops low the link value is set to zero and the variable maintains it's last value.





There is a a Project Setting in Unity which will maintain the output state of an EF when EN goes low. By default this setting is not selected.
To maintain the output state of a disabled EF go to Tools/Project Settings/Program/Language Common. Select "Maintain Output Links on Disabled EF or EN=0"