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[SOLVED] Scanning data in DB by using indirect addressing

Created by: Matilda at: 4/4/2011 11:20 AM (17 Replies)

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4/26/2011 6:11 PM	Rate (0)
Aret Posts: 2348 Rating: (264)	Well, place the new version of code here - can check it:^)
Aret Posts: 2348 Rating: (264)
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4/27/2011 6:37 AM	Rate (0)
Matilda Posts: 53 Rating: (1)	Ok, here it is! -------------------------------- OPN DB200 L P#0.0 LAR1 L 100 loop: T MW20 L DBW [AR1,P#0.0] T #VAR_2 L P#1.0 +AR1 //Comparisons start L #VAR_2 L W#16#3136 ==I JCN _001 A DB130.DBX1.0 _001: NOP 0 //Comparison ends L MW20 LOOP loop -------------------------------- The thing I don't understand is why it works in other CPU and not in the other...
Matilda Posts: 53 Rating: (1)
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4/27/2011 8:53 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/4/2024 Posts: 3024 Rating: (1054)	Hello Matilda The following twothings stick out in your logic: 1.) The command "A DB130.DBX1.0" will open DB 130 which - once executed - will stay open for the rest of the loop since DB200 is opened outside the loop. 2.) You increment AR1 by only 1 byte from one loop to the next but do access WORD variables via "L DBW [AR1,P#0.0]" which doesn't make too much sense to me(I'dexpect to see AR1 incresed by 2 Bytes per loop). Anyhow, below is my idea of your logic (not tested, so please try for yourself if it gives you the result you are after): LAR1 P#0.0 L 100 loop: T MW20 OPN DB200 // Open DB 200 L DBW [AR1,P#0.0] //Comparisons start L W#16#3136 ==I JCN _001 A DB130.DBX1.0 // DB130 is opened! _001: NOP 0 //Comparison ends +AR1 P#2.0 // bump AR1 by 2 Bytes to point to the next WORD L MW20 LOOP loop Notes: - DB200 must be at least 200 Bytes (100 Words) long. - Make sure that the logic between Comparison start and end does NOTchange AR1 (see HERE for more). - I prefer touse a TEMP variable for the Loop counter instead of MW20 (but either will work) I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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This contribution was helpful to 1 thankful Users Matilda

4/28/2011 8:32 AM	Rate (0)
Matilda Posts: 53 Rating: (1)	Uhh... Please forgive my foolishness_{rookie in plc-programming, as you probably already guessed}!! Didn't realize that A would open a DB... Now it seems to work, after I made the changes as fritz suggested. Thank you very much!!!
Matilda Posts: 53 Rating: (1)	Last edited by: Matilda at: 4/28/2011 8:36 AM But am I too wrong in my thinking, if I want to jump from word to another word and I move just byte forward, since aren''t the words like DBW 0 = bytes 0 & 1, DBW 1 = bytes 1 & 2 etc..?
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4/28/2011 11:18 AM	Rate (0)
MM1234 Posts: 270 Rating: (53)	Matilda But am I too wrong in my thinking, if I want to jump from word to another word and I move just byte forward, since aren''t the words like DBW 0 = bytes 0 & 1, DBW 1 = bytes 1 & 2 etc..? I think you are right, if you want to find a sequence of 2 words rightnext toeach other, you gotta proceed in a step of 1 word as you do and always load2 words from that point to compare, otherwise if you search for i.e. AB in a sequence CABC would miss it, 'cause if you would increase the address by 2 words, you would read CA and BC, but wouldn't read the AB inbetween. So you're doin' it right. I think that fritz just missed that requirement, because it's true that in general it doesn't make much sense.
MM1234 Posts: 270 Rating: (53)
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4/28/2011 11:55 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/4/2024 Posts: 3024 Rating: (1054)	MM1234's is correct (thanks MM1234),I did neglect to read thefollowing requirement from your orignal post: "The data in db is in 'CHAR' datatype and theres 100 bytes of content. But I need to look for 2 CHAR at the same time" In that case, do only"+AR1 P#1.0" to bump AR1 by one byte and do only 99 Loops. Having said that, if you were to copy your array of CHAR's into another DB and add thetwoString header bytesbefore it(max lenght and actual lenght, make both 100), you couldusethe IEC "FIND" String Function (default number is FC11 in the IEC library) to "find" the position of your search String within the main String (food for thougth anyhow which may come in handy in the future).
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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4/28/2011 12:00 PM	Rate (0)
MM1234 Posts: 270 Rating: (53)	Good point about the 99 iterations only, fritz, I always forget about stuff like that when I program and then sometimes spend loads of time searching for the error.
MM1234 Posts: 270 Rating: (53)
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5/6/2011 8:31 AM	Rate (0)
Matilda Posts: 53 Rating: (1)	Thanks guys for your help!
Matilda Posts: 53 Rating: (1)
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This contribution was helpful to 3 thankful Users S_Moderator fritz MM1234

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