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Old February 21st, 2011, 09:28 AM   #1
Ned_Flanders
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S7 datablock data types

While attempting to add a couple of functions I have found a discrepancy between the data types in a datablock between the running program and the backup copy the manufacturer left.

Can I online edit the data types rather than change and download the whole block?

The datablock contains lots of machine setting values and I don't want thes to default to "Zero"!!!

Thanks, Mark
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Old February 21st, 2011, 09:52 AM   #2
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No, you cannot change the declaration and keep the actual online values.
This is one of the most irritating deficiencies of STEP7.

I suggest that you change the data types in the offline project, but just make sure that the location of variables dont change.
Change from WORD to INT or DWORD to DINT or DWORD to REAL will be OK.
Then do not download this modified DB to the PLC.

You can then at a later time carefully update the offline DB's actual values with the online DBs actual values.
When everything lines up with the correct values and types, do a download to the PLC.
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Old February 21st, 2011, 10:43 AM   #3
L D[AR2,P#0.0]
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Quote:
Originally Posted by markie View Post
While attempting to add a couple of functions I have found a discrepancy between the data types in a datablock between the running program and the backup copy the manufacturer left.
Are the data types that are different the same length e.g. word/int or dword/dint ?
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Old February 21st, 2011, 11:52 AM   #4
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Quote:
Originally Posted by L D[AR2,P#0.0] View Post
Are the data types that are different the same length e.g. word/int or dword/dint ?
Unfortunately, No! Running copy is "INT" and backup "DINT". I can't really understand why they are different!
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Old February 21st, 2011, 12:09 PM   #5
JesperMP
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Maybe several DINTs have been changed into double the number of INTs.

Is the size of the DB in bytes the same as before ?
Or are the modifications at the end of the DB ?
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Old February 21st, 2011, 01:19 PM   #6
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Originally Posted by JesperMP View Post
Maybe several DINTs have been changed into double the number of INTs.

Is the size of the DB in bytes the same as before ?
Or are the modifications at the end of the DB ?
You are right - the block is the same size.

I can work around the problem - just dont want to loose 7 years worth of settings!!!
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