Retentivity Configuration

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When designing a PLC application, it is important for the PLC user to understand the different types of memory in the PLC. Three types of memory are used by the Mikrodev PLC; RAM, SRAM and FLASH memory.

SRAM memory can be configured by the PLC user as either retentive memory. SRAM is powered by internal battery when PLC external power is off.

Retentive memory is memory that is configured by the user to maintain values through a power reset. Non--retentive memory is memory that is configured by the PLC user to clear data after a power reset.

The default behaviour of the blocks in Mikrodev PLC is non-retentive. You need to select "Retentive" option to make the block use retentive memory.

retentiv2.png retentiv3.png retentiv4.png
If “Retentive” is not selected, it does not make any difference whether you select “Load Initial Value” or not. 

On Power Reset: The device will load the “Register Initial Value” into the register. 

On Project Upload: The device will load the “Register Initial Value” into the register.

On Power Reset: The register will preserve the latest value. 

On Project Upload:

A-    If there are any changes in the project like adding/removing retentive blocks, the “Register Initial Value” will be written on the register after boot.

B-    If there are minor changes on the project like parameter update or add/remove lines, the register will preserve the latest value after boot 

On Power Reset: The register will preserve the latest value. 

On Project Upload: “Register Initial Value” will be written on the register

Note: You can add maximum 256 retentive blocks on the device. You can check total retentive block count on the project using Mikrodiagram Tools>Show Project Info.