Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 67598995, Entry date: 03/23/2016

What are the advantages of using symbolic addressing for S7-1500 in STEP 7 (TIA Portal)?

  • Entry
  • Associated product(s)
With symbolic addressing you can program without having to worry about the internal data storage. The program code is clearer and easier to read.

In this entry we deal with the topic of "Universal definition and utilization of symbols" and the different ways of proceeding in STEP 7 V5.x and STEP 7 (TIA Portal).

Procedure in STEP 7 V5.x
In order to improve the readability of your programs, you allocate easily understandable names for your operands that you

  • Define as variables in data blocks or
  • Assign to the memory addresses of the inputs and outputs, markers, timers and counters in the symbol table.

After input of the address in the LAD/STL/FBD Editor the associated symbol is displayed automatically. Using "Address priority" in the block folder properties you can set whether after making a change in the symbol table the symbol or the absolute value has priority when you open the blocks. More information about this is available in Entry ID: 12412995.

When using symbolic programming there might be some cases when performance is impaired, for example when programming with user-defined data types (UDT). You can increase performance through absolute access to the address of the operand or parts of the operand, bits of a word, for example. However, at some time or other the program becomes unclear because of this and you have to make additional comments.

Procedure in STEP 7 (TIA Portal)
The SIMATIC S7-1500 provides much better performance than the SIMATIC S7-300/S7-400. To benefit from this we recommend you to enable optimized block access for all the blocks of the program and generally to program symbolically. You can benefit most from the S7-1500 functions using optimized blocks. Information about optimized blocks is available in Entry ID:67655611.

The data elements of the data blocks with optimized block access receive only one symbolic name in the declaration but no fixed address in the block. The elements are automatically arranged in the available memory area of the block so that its capacity is optimally used.

Fig. 01

You have the following advantages through using symbolic addresses:

  • It is easier to read the programs, which in turn means that you need less comments in the program
  • Input of the symbols is supported by IntelliSense in the TIA Portal
  • More powerful data access
  • Less program errors type safety (the validity of data types is checked for each access)
  • Automatic updating of the tag names at all points of usage in the user program
  • Storage of the program data does not have to be managed manually (absolute addressing)
  • No manual optimization necessary because of performance or program size.

Further Information
More information is available in the system manual "STEP 7 Professional V13 SP1", under: