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What is "Unsaved Declared Data" on Unity Pro Memory Usage Screen?

Published date: 25 January 2019

Goals and Symptoms
The "Memory Usage" screen on Unity Pro for M580 CPUs shows a type of user data: "Unsaved Declared Data"

Facts and Change
Unity Pro v10.0 or later, BMEP581020, BMEP582020, BMEP583020, BMEP584020, BMEP582040, BMEP583040, BMEP584040, BMEP585040, BMEP586040, BMEH582040, BMEH584040, BMEH586040,   

Causes and Fixes
The question and answers bellow explain what is the "Unsaved Declared Data".
1. What is "Unsaved Declared Data"?
Unsaved Declared Data are EFBs and DFBs variables that the user de-selected the "retain" option on data-editor when configuring a BMEx586040 CPU.
For other Modicon M580 CPUs, this attribute "retain" is read-only. It is selected by default and cannot be de-selected.

2. Can the user manage "Unsaved Declared Data"?
Yes, while programming a BMEx586040 on Unity Pro, the user can choose if the variable value will persist after a warm start of the CPU.
3. Is there a difference between how the "Unsaved Declared Data" is managed during Warm and Cold Start?
You can see below the behavior for both type of Start.
Selected retain: Variable data persists and is applied to the variable after a warm start.
De-selected retain ("Unsaved Declared Data"): Variable data is lost after a warm start; the variable value is reset.
In the event of a cold start of the CPU, both retained and non-retained data is reset.
4. Is this area of memory impacted by the users selections of "Update Initial Value with Current Values"?
No, it isn't impacted by "Update Initial Value with Current Values".

Additional Information: What is the meaning of Warm or Cold Re/start in PLC CPU?


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