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Entry type: FAQ Entry ID: 12412995, Entry date: 05/14/2007

What influence does the choice of address priority have when changing names in the symbol table and in the block editor?

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Configuration Notes:
Via "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. The table below describes the effects of the statements in the LAD/STL/FBD editor after making a change in the symbol table. If, for example, the block contains the statement "U Symbol_A", where in the symbol table Symbol_A is defined for the absolute value E0.1, then the setting of the address priority after the change in the symbol table has the following effect:

Address priority

Change of the assignment "Symbol_A > E0.1"

Statement after opening the block Explanation
Absolute value Symbol_A > E0.2 U E0.1 The absolute value E0.1 is displayed in the statement, because there is no longer any symbol assigned to it.
Absolute value Symbol_B > E0.1 U Symbol_B Displayed in the statement is the new symbol for the absolute value E0.1 that continues to be valid.
Symbol Symbol_A > E0.2 U Symbol_A The statement remains. A message about the change symbol assignment is displayed.
Symbol Symbol_B > E0.1 U Symbol_A

The statement is marked as defective (red font), because Symbol_A is no longer defined.

The table below describes how to set the address priority in the SIMATIC Manager.

No. Procedure:
1 Right-click the block folder and in the pop-up menu that is displayed you open the "Properties".
2 In the "Properties - Block Folder Offline" dialog select the "Address priority" tab.
3 Fig. 01 shows the dialog for setting the address priority in STEP 7 V5.2 and higher, where you can set the address priority either to Absolute value or to Symbol.

Fig. 01

The four choices have the following meanings:

  • With the address priority "Absolute value", after changes in the DB, fully qualified symbolic DB accesses in the code are retained with the name last saved. This means that with complete symbolic DB accesses in the code the symbol has priority.
  • An actual parameter is assigned to the formal parameter that has the same symbol as the formal parameter to which the actual parameter was assigned the last time saved - if that is possible with the data type and parameter type concerned. This means that when a block is added to the interface of a block, the existing actual value provisions are not lost. STEP 7 remembers the previous assignment.

More information is also available in the STEP 7 Online Help under "Setting the Address Priority (Symbolic/Absolute)".

4 Note on STEP 7 V5.0:
Open the "Properties - Block Folder Offline" dialog as described under No. 1. In the "Blocks" tab you can set the address priority to either "Absolute value" or "Symbol".

Fig. 02

General notes:

  • Please close all the blocks before switching to Symbolic or Absolute value, otherwise when you save the blocks, the address priority is reset to the original value before the blocks were opened.
  • If the address priority is set to "Absolute value" and you have subsequently changed addresses in the symbol table, then to activate these changes you should change the address priority to "Symbol".
  • If the address priority is set to "Symbol" and you have subsequently changed a symbol in the symbol table, then to activate this change you should change the address priority to "Absolute value".
  • If you open a project that has not yet been opened with STEP 7 V5.2 or higher, then the project is set to the previous procedure. If you wish to benefit from the advantages of one of the newer versions, then change the settings to the new version required.

Symbol assignment

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