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How to read/write from Data Block (DB)

Created by: trungchanhvo at: 10/6/2011 4:52 PM (10 Replies)

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10/6/2011 4:52 PM	Rate (1)
trungchanhvo Posts: 10 Rating: (1)	Hi all, I'm studying S7-300. I have question about DB. I want to write data from "Analog Input" to DB1 and read data from DB to "Analog Output" . But i dont know what i do. Please help me. Thanks a lot.
trungchanhvo Posts: 10 Rating: (1)
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This contribution was helpful to 1 thankful Users qwemx

10/6/2011 5:19 PM	Rate (1)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 11/18/2024 Posts: 5697 Rating: (715)	hello, That's not that hard to do. In stl use the L and T command. [code] L PIW 220 T DB1.DBW 2 [/code] This loads the input value in db1 word 2, your db must have this word. For the output you can do the same. [code] L DB1.DBW4 T PQW 220 [/code] in fbd you can use the move instruction. Make sure your DB is made correctly. Regards, Marcjan
	Last edited by: Marcjan at: 10/6/2011 5:19 PM Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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10/6/2011 5:25 PM	Rate (2)
miami Platinum Member Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (328)	Use L (load) and T (transfer) like this: [code]L #analog value TDB1.DBW 54[/code]loads the variable analog_valueand transfers it indataword 54(Byte 54 and 55) in the data block 1 or like this [code]OPN DB 1 L PIW 72 TDBW 22[/code]selects/opens DB 1, loads the periphery input word 72 and transfers it into data word 22 (of the actual open DB) And to read from DB just in the other direction: [code]LDB1.DBW 54 T#analog value_out[/code]or[code]OPN DB 1 L DBW 22 TPQW 72[/code]
	Last edited by: miami at: 10/6/2011 5:25 PM
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10/7/2011 1:42 PM	Rate (0)
trungchanhvo Posts: 10 Rating: (1)	Thanks a lot. i have a question. If i propram by LAD, i should used what command is. i trying MOVE but its wrong. So, i can propram by LAD to Read or Write data to Data Block (DB). Example, i receive data from Analog input, and write to DB1.DBW1. And the same with Read data from DB1.DBW1. Thanks.
trungchanhvo Posts: 10 Rating: (1)
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10/7/2011 2:41 PM	Rate (1)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 11/18/2024 Posts: 5697 Rating: (715)	Hello, The Move instruction should work, have you created a db with the varables of the type word? See picture for move instruction in ladder. Regards, Marcjan Attachment lad.JPG (2628 Downloads)
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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10/7/2011 3:36 PM	Rate (0)
trungchanhvo Posts: 10 Rating: (1)	Thanks for your help. i write wrong structure command. i have problem, does every DB memory have a address register? Because i want to read data step to step from DB1.DBW0 to DB1.DBW10 for each application. for example, i have "N" interger numbers, are stored in DB1, i caculator average value of "N" interger numbers. ( "N" is define by user from variable table)
trungchanhvo Posts: 10 Rating: (1)
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10/7/2011 5:55 PM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 11/18/2024 Posts: 5697 Rating: (715)	Hello, There are many discusions here about calculation averege, here is one /tf/WW/en/Posts/57980 There are some working examples in it. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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3/30/2013 9:53 AM	Rate (0)
SANDYA Posts: 2 Rating: (1)	HELLO, I WANT TO MOVE (1234) IN TO DB4.DBW[1234] MEANS I HAVE ONE ANALOG VALUE AND I WANT TO MOVE THAT INTO DB BUT ADRRESS FOR THAT WILL BE ACCORDING TO ANALOG VALUE, IS THERE IS ANY POSSIBILITY TO DO THE SAME. LOOK AT THE IMAGE AND PLZ HELP ME OUT... Attachment MOVE.JPG (1422 Downloads)
SANDYA Posts: 2 Rating: (1)	Last edited by: AutoGen_335830 at: 3/30/2013 9:58 AM
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3/30/2013 11:49 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	AutoGen_335830 HELLO, I WANT TO MOVE (1234) IN TO DB4.DBW[1234] MEANS I HAVE ONE ANALOG VALUE AND I WANT TO MOVE THAT INTO DB BUT ADRRESS FOR THAT WILL BE ACCORDING TO ANALOG VALUE, IS THERE IS ANY POSSIBILITY TO DO THE SAME. LOOK AT THE IMAGE AND PLZ HELP ME OUT... Hello, For doing such a thing, you need to indirect addressing.For more information on indirect addressing refer to the following FAQ: STEP 7 -- Creating S7 programs -- Indirect Addressing OPN DB 1 L L#100 SLD 3 LAR1 L IW [AR1,P#0.0] // or PIW[AR1,P#0.0] T DBW [AR1,P#0.0] Best regards Hamid Hosseini
	Last edited by: hdhosseini at: 3/30/2013 5:31 PM Last edited by: hdhosseini at: 3/30/2013 5:19 PM Demo Channel on Youtube
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1/13/2016 9:40 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by ICOMR is split to a separate thread with the subject Transfer inputs & outputs to DB, failure "The bit is not authorised for this instruction". Best regards Min_Moderator

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