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Siemens AG
Entry type: FAQ, Entry ID: 68015630, Entry date: 04/21/2017
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How is the declaration table for global data blocks structured in STEP 7 (TIA Portal)?

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The display of the declaration table varies depending on the type of block and access.

Description
In STEP 7 (TIA Portal) you have the optimized access and standard access available for accessing data values in data blocks.

Data block access types
If you insert a new global data block for the S7-300/S7-400 in the project navigation, it is given the "Standard" access type.
Fig. 1 shows the declaration table of a global data block for an S7-300/S7-400 CPU with "Standard access".
 


Fig. 1

In STEP 7 (TIA Portal), if you add a new global data block for the S7-1200/S7-1500, it is stored automatically in the "Program blocks" folder with "optimized block access".

In comparison with the data blocks with the "standard" type of access, the data blocks with "optimized" block access do not have the "Offset" column because they do not have a defined structure. The retain behavior of data blocks with the "standard" type of access cannot be set for individual variables. The retain behavior setting applies for all the variables of the data block.

Fig. 2 shows the declaration table of a global data block for an S7-1200/S7-1500 CPU with "optimized block access".
 


Fig. 2

If you disable the "Optimized block access" function, the retain settings change in the block interface. The block must be recompiled after each change.

Note
To achieve better performance we recommend that you always program symbolically with the S7-1200/1500 and use the "Optimized block access" setting.

Columns of the declaration table "Show/Hide"
You can show and hide columns in tables as required. The number of columns displayed varies depending on the CPU family.
Proceed as follows to show/hide table columns in your global data block:

  1. Right-click in a column header.
  2. In the pop-up menu you select the menu command "Show/Hide".
  3. In the drop-down menu that opens you enable or disable the listed columns by setting or removing a check mark in the check box of the column concerned.


Fig. 3

Further Information
More information is available in our entries and manuals under:

Creation Environment
The screens in this FAQ response were created with STEP 7 (TIA Portal) V14.