Hi,

Sorry for making this topic active after so many years. 

I am experiencing problems with declaring variable from Data Block in Symbol Table. 

For example, I declare in Data Block (DB1) variable 0.0, name VAR, type WORD. In Symbol Table when I enter DB1.DBW0 for an address I get message that wrong data type is used. 

As I could understand from this topic, DB1.DBW0 should be written in the address column of Symbol Table. Am I wrong?

Any ideas how to solve this?

Thanks in advance.

Regards,

Dimitrije

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Split from Symbol Table and DB Symbolic Address.

Dimitrije

Hi,

Sorry for making this topic active after so many years. 

I am experiencing problems with declaring variable from Data Block in Symbol Table. 

For example, I declare in Data Block (DB1) variable 0.0, name VAR, type WORD. In Symbol Table when I enter DB1.DBW0 for an address I get message that wrong data type is used. 

As I could understand from this topic, DB1.DBW0 should be written in the address column of Symbol Table. Am I wrong?

Any ideas how to solve this?

Thanks in advance.

Regards,

Dimitrije

Hello.

In general there are two types of DBs:
1) A DB that is linked to an FB is called an instance DB.
2) An unlinked DB is called a global DB.

The symbol name of the DB itself (DB1 in your case), is saved in the symbol table. An instance DB should already be mentioned there where the linked FB is mentioned.

The symbol name of the element inside the DB is not named in the symbol table. In both DB types the names of the elements looks like parameters.
1) The elements of an instance DB is named from the FB
2) The elements of the global DB is named within the definition of the DB.

Take care thar naming overlapped memory is not possible. Naming DB1.DBW0 cannot be done if the overlapping DB1.DBX0.0 to DB1.DBX1.7 was already named. The same applies for DB1.DBB0 and DB1.DBD0 for example. Overlapped memory areas for M-memory can be named.

Assume myWord is the symbol defined for DB1.DBW0. The program can still use access the internal bits but by use of absolute addressing like DB1.DBX1.4   .

Do these notes help?
~

qwazee

Hello.

In general there are two types of DBs:
1) A DB that is linked to an FB is called an instance DB.
2) An unlinked DB is called a global DB.

The symbol name of the DB itself (DB1 in your case), is saved in the symbol table. An instance DB should already be mentioned there where the linked FB is mentioned.

The symbol name of the element inside the DB is not named in the symbol table. In both DB types the names of the elements looks like parameters.
1) The elements of an instance DB is named from the FB
2) The elements of the global DB is named within the definition of the DB.

Take care thar naming overlapped memory is not possible. Naming DB1.DBW0 cannot be done if the overlapping DB1.DBX0.0 to DB1.DBX1.7 was already named. The same applies for DB1.DBB0 and DB1.DBD0 for example. Overlapped memory areas for M-memory can be named.

Assume myWord is the symbol defined for DB1.DBW0. The program can still use access the internal bits but by use of absolute addressing like DB1.DBX1.4   .

Do these notes help?
~

Hi qwazee,

Thanks for your answer. Lots of useful information is there.

I forgot to mention that I use global DB, so it's not linked to an FB.

Things about overlapped memory are perfectly clear.

One thing I want to sort out is about this part:

"The symbol name of the element inside the DB is not named in the symbol table. In both DB types the names of the elements looks like parameters.
1) The elements of an instance DB is named from the FB
2) The elements of the global DB is named within the definition of the DB"

So it's not possible to declare separate parameters of DB in Symbol Table? DB1 can be declared in Symbol Table, but its parameter DB1.DBW0 can not?

Regards,

Dimitrije

Dimitrije

 <snip>

So it's not possible to declare separate parameters of DB in Symbol Table? DB1 can be declared in Symbol Table, but its parameter DB1.DBW0 can not?

</snip>

Hello.

Yes you can assign symbol names for the elements inside the global DB. The names are not stored in the symbols table. The names are stored inside the DB.

Open the DB and view the DB. The symbol names are done much in the same way the parameters are done in an FC / FB. You should expect something like:

Have a look at chapter 11 of the manual:
SIMATIC Programming with STEP 7 V5.5

~

qwazee

Hello.

Yes you can assign symbol names for the elements inside the global DB. The names are not stored in the symbols table. The names are stored inside the DB.

Open the DB and view the DB. The symbol names are done much in the same way the parameters are done in an FC / FB. You should expect something like:

Have a look at chapter 11 of the manual:
SIMATIC Programming with STEP 7 V5.5

~

 Hi,

I was probably not enough clear with my question. 

When I assign symbol names for elements inside the global DB, can I do it also in Symbol Table?

For example, 

In DB1 I declare: 0.0 (address) ; varName (Name) ; WORD (Type) ; W#16#0 (Initial Value)

Then in Symbol Table I assign: varName (Symbol) ; DB1.DBW0 (Address) ; WORD (DataType)

So, in OB1 when I want to use DB1.DBW0 address I simply type "varName" instead of typing DB1.DBW0. In that way, program will use DB1.DBW0 address (because I typed "varName" and that name is assinged to DB1.DBW0 in Symbol Table) and DB1.DBW0 is declared in DB1.

Is it possible?

Regards,

Dimitrije

What you are asking for is called an alias in the Rockwell world.
Siemens does not have that. 

Okay qwazee, thanks for information and help.

Regards,

Dimitrije