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instance db

12/16/2011 4:58 PM	Rate (0)
saeedplc Posts: 288 Rating: (4)	hello. i need to know that if it is possible to read and write value to an instance db from a fc? suppose that there is instance db1 and in fc10 i write this program: l db1.dbw0 l 20 +i t db1.dbw0 best regards.
saeedplc Posts: 288 Rating: (4)
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12/16/2011 5:13 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	yes, of course. you can read/write frominstance db as it was global db.
Marko Bursic Posts: 1410 Rating: (154)
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12/16/2011 6:02 PM	Rate (0)
nbk Posts: 197 Rating: (3)	But aren't Shared DBs known as global DBs and the Instance DBs are meant for their particular FBs alone? ........ Unless I completely misunderstand this !! Regards
nbk Posts: 197 Rating: (3)
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12/16/2011 7:08 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	nbk But aren't Shared DBs known as global DBs and the Instance DBs are meant for their particular FBs alone? ........ Unless I completely misunderstand this !! Regards That's true, but you can access all those variables that were declared as STAT, as well as IN,OUT,IN_OUT they are all allocated in instance DB. I do usualy define only very basic inputs and outputs of a FB, in most cases in/out peripheral bits,words,...that are connected to physical in/out. All other variables of FB I do access trough instance DB. In such way you don't copy variables from output of a FB to marker and then from marker to another FB.
Marko Bursic Posts: 1410 Rating: (154)
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12/17/2011 2:23 PM	Rate (0)
nbk Posts: 197 Rating: (3)	Agreed Marko Bursic. (I misunderstood your 2nd post / text which I thought is equating Instance DBs with Global DBs - ".....you can read/write frominstance db as it was global db. ") Regards
nbk Posts: 197 Rating: (3)
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12/17/2011 10:15 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 1/5/2026 Posts: 6892 Rating: (1368)	Dear friends , Just add a point on writing constant permanent values on IN_OUT parameters in a Function Block may be problematic. Check the following link for a sample case: Why writing permanent values on MAN_ON,MAN parameters of FB58 is not recommended Best regards, Hamid Hosseini
	Demo Channel on Youtube
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