Siemens Memory Specifications download pdf (Page 50)

3 General Programming

3.6 Symbolic addressing

Programming Guideline for S7-1200/1500

V1.2, Entry ID: 81318674

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Figure 3-26: Indirect field access

SCL:

LAD / FBD:

Advantages

 Simple access since the data type of the ARRAY elements is irrelevant for the

access.

 No complicated pointer creation required

 Fast creation and expansion possible

 Useable in all programming languages

Properties

 Structured data type

 Data structure made of fixed number of elements of the same data type

 ARRAYs can be created also multi-dimensional

 Possible indirect access with runtime tag with dynamic index calculation at

runtime

Recommendation

 Use ARRAY for indexed accesses instead of pointer (e.g. ANY pointer). This

makes it easier to read the program since an ARRAY is more meaningful with

a symbolic name than a pointer in a memory area.

 As run tag use the INT data type as temporary tag for highest performance.

 Use the “MOVE_BLK” instruction to copy parts of an ARRAY into another one.

 Use the “GET_ERR_ID” instruction to catch access errors within the Array.

Note

You will find further information in the following entry:

How do you implement an array access with an S7-1500 with variable index?

http://support.automation.siemens.com/WW/view/en/67598676

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Siemens Memory Specifications Page 50