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Created by: trap_64h at: 1/24/2007 12:39 AM (20 Replies)

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1/24/2007 12:39 AM	Rate (0)
trap_64h Posts: 3 Rating: (0)	What is the difference (size, speed) between: L DB1.DBW0 and OPN DB1 L DBW0 trap_64h
trap_64h Posts: 3 Rating: (0)
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1/24/2007 3:43 PM	Rate (3)
Denilson Pegaia Platinum Member Joined: 9/23/2005 Last visit: 11/19/2024 Posts: 4353 Rating: (1452)	Hi, alone, the both options are identicals. L DB1.DBW0= OPN DB1 + L DBW0 However, if you have many DB access, de second option is economical: L DB1.DBW0 L DB1.DBW2 L DB1.DBW4 bether is (less bytes / instructions) OPN DB1 L DBW0 L DBW2 L DBW4 Take acount, however, that the first representation is symbolically possible, the second not: L DB1.DBW0 = L banane.apple (DB1= banane; DBW0 = apple) <> of OPN banane L DBW0 (DBW can not be expressed as "apple" whit out the presence of the respective DB "banane")
	Last edited by: Pegaia at: 1/24/2007 3:56 PM Denilson Pegaia Siemens Industry Sector Technical Support
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1/25/2007 9:35 AM	Rate (0)
trap_64h Posts: 3 Rating: (0)	[quote user="Pegaia"] bether is (less bytes / instructions) OPN DB1 L DBW0 L DBW2 L DBW4 Interesting... Above instructions though are equivalent to: L DB1.DBW0 L DBW2//read from DB1 DBW2 L DBW4//read froom DB1 DBW4 and L DB2.DBW0 L DBW2//read from DB2 DBW2 L DBW4//read froom DB2 DBW4 Is this correct? Thanks, trap#64h
trap_64h Posts: 3 Rating: (0)
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1/25/2007 9:53 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 11/19/2024 Posts: 8770 Rating: (1171)	Hello trap_64h, You'll have first to open Datablock: So you must use the following instructions: Opn DB 1 // open the desired Datablock L DBW 0 // you nowuse DB1.DBW0 L DBW 2 // DB1.DBW2 L DBW 4 Opn DB 2 L DBW 0 // you nowuse DB2.DBW0 L DBW 2 So you must use the instructions like Pegaia told. Best regards, Wizard
	Last edited by: Wizard at: 1/25/2007 9:55 AM
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1/25/2007 11:33 AM	Rate (1)
Aret Posts: 2348 Rating: (264)	Actually such code OPN DB5 L DB1.DBW0 L DBW2 would load DBW 2 from DB1. But this is not too good working in such manner. Programm would much more inderstandable if you'll write OPN DB1 L DBW0 L DBW2
Aret Posts: 2348 Rating: (264)
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This contribution was helpful to 1 thankful Users Berg

1/25/2007 4:10 PM	Rate (1)
Dec Gold Expert Joined: 5/19/2006 Last visit: 10/23/2024 Posts: 549 Rating: (107)	Very good observation Aret!!! If you access a DB structure using absolute addressing you have to reload AR1 (OPN DBx) again, because L DBx.DByz altered AR1. L DB1.DBW2 is a pseudo instruction made up by MC5 opcode OPN DB1 (0x20, 0x01) and L DBW2 (0x7E, 0x42, 0x00, 0x02). Dec [quote user="Pegaia"] Take acount, however, that the first representation is symbolically possible, the second not: This is a STEP7 LAD/STL editor problem, the code is identical 100%
	Last edited by: Dec at: 1/25/2007 4:36 PM
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2/8/2007 3:11 PM	Rate (0)
Marcio R. Santos Silver Member Joined: 12/5/2005 Last visit: 9/25/2024 Posts: 239 Rating: (9)	Hi, L DB1.DBW0 L DB1.DBW2 L DB1.DBW4 bether is (less bytes / instructions) OPN DB1 L DBW0 L DBW2 L DBW4 But the use of L DB1.DBW0 is more security than OPN DB1 L DBW0 if you use programs with several OBs times or OBs interruption. Example: //////////////////////////////////////////////// OB1: OPN DB1 L DBW0 //////////////////////////////////////////////// //////////////////////////////////////////////// OB35: OPN DB2 L DBW0 //////////////////////////////////////////////// The sequence below, is executed in the same cycle: 1. CPU execute theOB1 OPN DB1 2. CPU call the OB35 OPN DB2 L DBW0 3. End of OB35 4. CPU return to OB1 L DBW0 In the step 4, the DBW0 read is the DBW0 of DB2 and not of DB1. OK?
	Márcio Santos www.marcioroberto.wordpress.com
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This contribution was helpful to 1 thankful Users Berg

2/11/2007 8:45 AM	Rate (0)
Dec Gold Expert Joined: 5/19/2006 Last visit: 10/23/2024 Posts: 549 Rating: (107)	[quote user="Marcio"] In the step 4, the DBW0 read is the DBW0 of DB2 and not of DB1. OK? I don't think so. Each task switch (OB1 -> OB35) saves all the CPU register bankof the current priority before switch to a task with higher priority. If you are confident that DBW0 is been read from DB2 let me know [:o] Dec

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This contribution was helpful to 1 thankful Users Berg

2/12/2007 8:14 AM	Rate (0)
Aret Posts: 2348 Rating: (264)	Agree with Dec - ACCUs, registers etc. are stored in stack on calling OB35 and restoring them when turning back - it's standart procedure for interrupts.
Aret Posts: 2348 Rating: (264)
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2/12/2007 12:14 PM	Rate (0)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 11/19/2024 Posts: 4796 Rating: (733)	[quote user="Dec"] ...reload AR1 (OPN DBx)... Ithink that OPN DBx changes content of the DB register.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
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