Technical data

Memory areas and retentive memory
2.2 Retentive memory areas
Structure and Use of the CPU Memory
14 Function Manual, 01/2013, A5E03461664-01
Tags from a global data block
In a global data block, you can define either individual tags from a block or all of its tags
collectively as retentive, depending on the setting for the "Optimized block access" attribute:
● "Optimized block access" activated: In the declaration table of the data block, you can
define individual tags as retentive.
Figure 2-5 Retentivity setting "Optimized block access" activated
● "Optimized block access" not activated: In the declaration table of the data block, you can
only define the Retentivity for all tags collectively.
Figure 2-6 Retentivity setting "Optimized block access" not activated
Tags from an instance data block of a function block
In STEP 7, you can define the tags from the instance data block of a function block as
retentive. Depending on the setting for the "Optimized block access" attribute, you can define
retentivity either for individual tags from a block or for all of its tags collectively:
● "Optimized block access" activated: In the interface of the function block, you can define
individual tags as retentive.
● "Optimized block access" not activated: In the instance data block, you can only define
the retentivity of all tags collectively.
Creation of a data block in the user program
You use the "CREATE_DB" instruction to create a data block in the user program.
Depending on the selection for the ATTRIB parameter, the generated data block either has
the property "retentive" or the property "non-retentive". Setting the retentivity for individual
tags is not possible here.
You can find additional information on the "CREATE_DB" instruction in the STEP 7 online
help under "PLC programming > References > References (S7-1200/1500) > Extended
instructions > Data block functions > CREATE_DB".