Retain and Persistent variables. Beijer Electronics X2 control

X2 control – Basic Start Up settings

SUEN284 2017-04

10 Retain and Persistent variables

The PLC functionality have support for storing non-volatile retain and persistent variables

Those variabels can be stored dynamically in two different modes:



Power-fail mode:

If the voltage drops below a hardware given threshold (that is, during a power loss or power dip), the system instantly copies all retain and persistent data defined in the PLC application from RAM into the battery backed SRAM.

They are verified and restored when the device is restarted.



Cyclic mode: the PLC is instructed to store all retain and persistent data directly into SRAM synchronously with every PLC cycle. This means, there is no restriction about the memory size and all device types can use the whole available memory, which is 128 kiB.

However, writing to the SRAM might increase the configured PLC cycle depending on the size of used retain and persistent data, because a SRAM is naturally slower then a

RAM.

Overview of Retain/persistant data configurations:

Refer to documentation for details:

“How to use Retain/Persistent data in CoDeSys on X2 control/motion/marine SC”

Persistent variables (non-volatile memory) can ONLY be declared in a special global variables list, which is assigned to an application. There might be only ONE such list per application.



Highlight Application .



Right click and select Add Object .



Choose PersistentVariables..

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X2 control – Basic Start Up settings



Command Table from CODESYS Online Help

SUEN284 2017-04

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“-“ = values gest initiated www.beijerelectronics.se

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