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S7-1200 DB access from function block

Created by: autom8 at: 11/4/2011 3:41 PM (10 Replies)

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11/4/2011 3:41 PM	Rate (0)
autom8 Regular Member Joined: 5/23/2008 Last visit: 2/4/2022 Posts: 8 Rating: (0)	How do you setup access to a DB in a function block with the DB number as an input to the function block. In s7-300 oneway this can bedone is bysetting input declartion as data type DB and use the OPN instruction then address directly the data in the db, DBX0.0 etc. Any ideas would be greatly appreciated!
	Last edited by: autom8 at: 11/10/2011 7:36 PM
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11/7/2011 1:29 PM	Rate (1)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 1/27/2023 Posts: 4176 Rating: (1323)	Hi, See the follow example. Indirect address, of DB3.DBX4.5, MW0=DB pointer; MD10=Bit pointer: L 3 T MW0 OPN DB[MW0] ... L 37 => 4*8+5 T MD10 A DBX[MD10]
	Denilson Pegaia Siemens Industry Sector Technical Support
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11/10/2011 4:56 PM	Rate (0)
autom8 Regular Member Joined: 5/23/2008 Last visit: 2/4/2022 Posts: 8 Rating: (0)	Pegaia Hi, See the follow example. Indirect address, of DB3.DBX4.5, MW0=DB pointer; MD10=Bit pointer: L 3 T MW0 OPN DB[MW0] ... L 37 => 4*8+5 T MD10 A DBX[MD10] Thanks for the sugestion, I originally posted this in the S7-1200 forum and failed to mention in the message that my questionis specific to the S7-1200.

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11/17/2011 3:22 AM	Rate (0)
autom8 Regular Member Joined: 5/23/2008 Last visit: 2/4/2022 Posts: 8 Rating: (0)	No ideas ? Have been working on a way around this for awhile myself, surely someone has come across a way to do this...

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11/17/2011 5:26 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 1/27/2023 Posts: 4176 Rating: (1323)	Hi, Maybe rest to us just wait for SP2 (where will come SCL)...
	Denilson Pegaia Siemens Industry Sector Technical Support
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9/24/2013 2:17 PM	Rate (0)
plcordoba Regular Member Joined: 1/8/2007 Last visit: 10/5/2022 Posts: 21 Rating: (1)	Hi all! I have TIA Portal V12 SP1 Update 2. I would like to know how to do this with scl for S7 1200. Anyone can help me? Thanks!!!

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9/24/2013 2:47 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/26/2023 Posts: 13079 Rating: (2121)	plcordoba Hi all! I have TIA Portal V12 SP1 Update 2. I would like to know how to do this with scl for S7 1200. Anyone can help me? Thanks!!! Use the peek instruction. Look at the help for how to provide the db # and offset values. Then you can loop through the DB a byte or word at a time.
	science guy
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9/24/2013 3:26 PM	Rate (0)
plcordoba Regular Member Joined: 1/8/2007 Last visit: 10/5/2022 Posts: 21 Rating: (1)	Thanks but I know peek/poke functions. What I want to know is how to access to data from instance DB or Global DB within FBs. For example (S7300/400): L #DB_Out T #AUX_DB AUF DB [#AUX_DB] UN DBX 30.3 S DIX 30.5

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9/24/2013 3:34 PM	Rate (1)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/26/2023 Posts: 13079 Rating: (2121)	plcordoba Thanks but I know peek/poke functions. What I want to know is how to access to data from instance DB or Global DB within FBs. For example (S7300/400): L #DB_Out T #AUX_DB AUF DB [#AUX_DB] UN DBX 30.3 S DIX 30.5 You already know the answer, peek/poke, as the only option for s7-1200. You want the STL version, you will want the s7-1500. All you need is the DB #. That said, with the portal software pushing us towards not using absolute address access and making truly universal logic programming, it seems like a revisit to the original need may help. If your logic is organized with the new way in mind, Siemens is putting the tools in place with the portal software, with custom plc datatypes, bit/byte slicing (using tag.x# and tag.b#), that should enable your problem to be solved without resorting to direct DB access. I find when I use the portal the way it was intended, it is much easier to reuse the code without any changes. When I deviate and use absolute access, my maintenance needs increase and code reuse is much more time consuming. I find bugs all the time that result from direct access. When I use custom plc datatypes, structures, dbname.tag, I find things just work out. Just a thought.
	science guy
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9/24/2013 5:15 PM	Rate (0)
plcordoba Regular Member Joined: 1/8/2007 Last visit: 10/5/2022 Posts: 21 Rating: (1)	Thanks for your reponse!

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