S7- Copying DB to DB

Nick B · Nov 9, 2008

Hello,
I want to copy a DB to a DB in S7. Any ideas. I don't want to do a BlockMove if Possible for speed considerations and I don't want to bother with DB length etc. I just want to clone a DB. I've looked in the system library and don't see anything appropriate.

Thx in advance.

L D[AR2P#0.0] · Nov 9, 2008

It's either SFC20 or make your own loop for the copy.

JesperMP · Nov 10, 2008

Maybe try SFC81 UBLKMOV. The difference between SFC81 and SFC20 seems mainly to be that it is "uninterruptible". Maybe that means that it works faster.
edit: The uninterruptible also means that it affects eventual interrupts.

What is it that you want to achieve ?
Does the DB that you want to clone to not exist before the cloning ?
Shall it exist in work memory only, in load memory only, or in both ?
The bit about that you dont want to bother about the length, does that mean that the cloning must be dynamically configured at runtime ?

Peter Nachtwey · Nov 10, 2008

JesperMP said:
Maybe try SFC81 UBLKMOV. The difference between SFC81 and SFC20 seems mainly to be that it is "uninterruptible". Maybe that means that it works faster.
edit: The uninterruptible also means that it affects eventual interrupts.

Uninterruptible means that there are no interrupts while UBLKMOV is active. That will delay any interrupts and the code inside like PIDs. This will adversely affect the derivative action. The UBLKMOV should be used by code outside the interrupts to copy code. This may be important if an interupt routine also copoes code to or from the same data.

PeterW · Nov 10, 2008

You can get the length of you block with L DBLG and create a block using one of the library FB's (don't have list so can't be specific).

Afraid in copying the actual data, its as per previous suggestion only.

Jeebs · Nov 10, 2008

PeterW said:
You can get the length of you block with L DBLG and create a block using one of the library FB's (don't have list so can't be specific).

Afraid in copying the actual data, its as per previous suggestion only.

Nice thing there and handy if you want to create your pointers on the fly.

But according to the help it only works on shared DB's. Not on instance DB's. Is this correct?

L D[AR2P#0.0] · Nov 10, 2008

What exactly are you referring to when you say it "only works on shared DB's" ?

Jeebs · Nov 10, 2008

L D[AR2 said:
What exactly are you referring to when you say it "only works on shared DB's" ?

"Description of instruction

L DBLG (load length of shared data block) loads the length of the shared data block into ACCU 1 after the contents of ACCU 1 have been saved into ACCU 2."

Help on STL on L DBLG.

L D[AR2P#0.0] · Nov 10, 2008

L DILG

Description of instruction

L DILG (load length of instance data block) loads the length of the instance data block into ACCU 1-L after the content of ACCU 1 has been saved into ACCU 2.

JesperMP · Nov 10, 2008

There are L DBLG and L DILG for shared DBs and instance DBs respectively.

:Too slow. Remind myself to spend more time on PLCS.NET !

Nick B · Nov 10, 2008

UBLOCKMOVE does not operate any faster (and has a 256byte limit). What I'm trying to achieve is as follows.

Due to a limitation in WinCC (V6.2) you cannot get at Instance DB's, I was trying to achieve a work around.

1. Export MultiInstance DB into XLS utility (no problem)
2. Import as Global DB into "twin" DB
3. Now WinCC can see it symbolically
4. Copy original DB into clone which WinCC will use to interface
5. Drop new DB onto original and execute.

It's more of a procedure to overcome a limitation in WinCC. In WinCC-Flex this would be no issue but for some reason this function is still not available with V6.2 or even V7.0. Rather silly considering flex has be able to do this since 2004.

PeterW · Nov 10, 2008

Don't know much about WinCC, but can you just call the IDB, DB to get WinCC to access it?

JesperMP · Nov 10, 2008

Thinking the same, it must be possible to create regular tags that point to the IDB, only you have to do it without symbols.
Is the problem more about getting the symbols ?
Dont know WinCC so much. How about using OPC ? I think that if you select to include all symbols, then also the the symbols for the IDBs will be generated.

S7- Copying DB to DB

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