Summary

When adding a new tag to read/writes to a datablock in a S7-1200 or S7-1500 CPU, optimized block access must be disabled. By turning off optimized block access, the data elements in the datablock got their own unique address.

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Procedure

Step 1: In TIA portal, right click on the datablock you want to access from AP Historian and select “Properties”.

Step 2: Go to the “Attributes” tab and untick “Optimized block access”. Click “Ok”.

Step 3: Now open the datablock and add data elements. The “offset” column shows the data element’s unique address and must be used in AP Historian to get a datablock value.

Step 4: Download the changes to the CPU.