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about direct db access from own fb

Created by: kosta at: 10/7/2009 5:25 PM (6 Replies)

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10/7/2009 5:25 PM	Rate (0)
kosta Advanced Member Joined: 2/17/2008 Last visit: 10/27/2024 Posts: 50 Rating: (4)	hello all, i know that accessing DB data is possible like " %DB9.DBX5.1 " .. but if you are in an FB block is it possible to access directly its own instance block without using simbols .. just like " %DIX5.1 " or something similar. ? reason for this question is that i want to keep my bits in word so i could shift them, bit i still need to access individualy any of those bits to check if it is on or off. regards
	Last edited by: kosta at: 10/7/2009 5:26 PM
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10/13/2009 12:46 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	Hi, when creating FB choose non-symbolic. Enter all your variables you need in FB and create instance DB. You can see there an offset. It's for the absolute addressing you need. e.g. DB1.dbx10.5 regards

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10/23/2009 5:29 PM	Rate (0)
kosta Advanced Member Joined: 2/17/2008 Last visit: 10/27/2024 Posts: 50 Rating: (4)	yes '..i know that accessing DB data is possible like " %DB9.DBX5.1 "' .. what i dont know is if you can acces bits in word field without say which DB you want to access .. but you just access DB of that FB you are in.. if FB1 is parametrised with DB1 .. i dont want to write db1.dbx5.1 .. i want to just state dbx5.1 .. and want plc to look intoFB1s own DB .. whichewer DB is parametrised to FB1. is it possible ?

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10/26/2009 8:58 AM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	No, sorry. thats not possible. You need to enter the DB. If you want to work inside FB and want to see some bits, you can do the workaround with Shift-Rotate and logical operations. But this is very complex.

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11/2/2009 4:28 PM	Rate (0)
glubb Posts: 26 Rating: (4)	Hello, isn't this the typical use case for a Instance DB? An instance DB stores the data and parameter of the FB. Now you can call this FB with several instances of a DB without knowing which DB is used when the FB is called...
glubb Posts: 26 Rating: (4)
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3/18/2010 4:41 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 11/4/2024 Posts: 4351 Rating: (1451)	Hi, The FAQ http://support.automation.siemens.com/WW/view/en/41512046 has a sample program that convert bool to word and vice versa. That could help you
	Denilson Pegaia Siemens Industry Sector Technical Support
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3/19/2010 10:53 AM	Rate (0)
Maha Posts: 118 Rating: (4)	kosta yes '..i know that accessing DB data is possible like " %DB9.DBX5.1 "' .. what i dont know is if you can acces bits in word field without say which DB you want to access .. but you just access DB of that FB you are in.. if FB1 is parametrised with DB1 .. i dont want to write db1.dbx5.1 .. i want to just state dbx5.1 .. and want plc to look intoFB1s own DB .. whichewer DB is parametrised to FB1. is it possible ? I am not sure weather i understood your question or not. But anyway i try to explain based on what i understood. if the DB is external DB, you can do in following way, first open the DB, thn directly use the bits. OPN DB5 A DBX0.0 // it means DB5.DBX0.0 =DBX1.0 if its instance DB (own DB of the particular FB), then you can directly use like A DIX0.0 =DIX1.0 For other DB
Maha Posts: 118 Rating: (4)
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