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SFC20-blkmov - how to be sure if operation did correct?

Created by: SuHu at: 2/20/2018 8:55 AM (6 Replies)

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2/20/2018 8:55 AM	Rate (0)
SuHu Silver Member Joined: 9/8/2016 Last visit: 8/22/2025 Posts: 198 Rating: (10)	Hi All, I've read so many topic abous SFC20 blkmov but still have some doubt. Thank you in advance for help. I want to use SFC20 in below code: AN M "HMI_start_copy" JC _001 CALL "BLKMOV" SRCBLK :=#SRCBLK_ANY RET_VAL:=MW10 DSTBLK :=#DSTBLK_ANY SET R M "HMI_start_copy" _001: NOP 0 The structure of any pointer is that i choose bytes as data type. The bytes amout is ~4000 (in manual there is no information about maximum bytes amount or something like that). I am copying DB values to the exact DB (structure in this DB are the same). The main question is: 1. How can i be sure that copying result was successed? 2. In my code i run (energised) SFC20 only for one scan. Is that solution is correct?

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2/20/2018 11:33 AM	Rate (3)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 7/10/2025 Posts: 1561 Rating: (540)	1, If the return value (error code) is 0, then you can take this as the correct operation of BLKMOV. Any other value than 0 indicates an error of some sort. 2. The BLKMOV will complete in one call, however, it can be interrupted during the copy by higher priority OB's, which could lead to inconsistent data in the destination address. If your data HAS to be copied as a consistent set then consider using UBLKMOV as this cannot be interrupted during the copy.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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This contribution was helpful to 5 thankful Users Prassanna G Rescobedo SuHu Md Gouse AutoGen_484192

2/21/2018 7:29 AM	Rate (0)
SuHu Silver Member Joined: 9/8/2016 Last visit: 8/22/2025 Posts: 198 Rating: (10)	Hi, @smiffy, thank you for replaying. Additional questions: 1. In my Simatic Step7 i do not have UBLKMOV block in SFC block library folder. How could i add this block to project? 2. If SFC20 instruction can be interputed by higher OB priority i don't see the reason to use this instruction at all?? My thinking is that - i am using instruction and i want to be sure that this instruction will run. Hope you understand my point of view. Is it possible that i do not have such OB's in my project? By myselft i do not configure them. Or maybe this are systems OB?
	Last edited by: SuHu at: 2/21/2018 7:32:00 AM
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2/21/2018 9:09 AM	Rate (0)
Hati Platinum Member Joined: 9/21/2012 Last visit: 9/10/2025 Posts: 4708 Rating: (510)	SuHu 1. In my Simatic Step7 i do not have UBLKMOV block in SFC block library folder. How could i add this block to project? UBLKMOV is a TIA Portal function, not found in old Step 7.

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2/21/2018 6:19 PM	Rate (0)
Rescobedo Silver Member Joined: 11/5/2012 Last visit: 8/14/2025 Posts: 490 Rating: (64)	Hello. UBLKMOV is SFC81. chapter 3.2 page 100 on this manual Take a look. Hope this helps. Regards.
	Last edited by: Jen_Moderator at: 2/22/2018 8:18:35 AM Optimized link.
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This contribution was helpful to 2 thankful Users Prassanna G SuHu

2/23/2018 7:36 AM	Rate (0)
SuHu Silver Member Joined: 9/8/2016 Last visit: 8/22/2025 Posts: 198 Rating: (10)	Thank you for advice. I check UBLKMOV and it seems that instruction is available for S7-300&400 in Step V5.4. I just put CALL SFC81 in my network and Instruction UBLKMOV appears in library. The biggest disadvantage for UBLKBMOV is that the max byte amount is 512. The other question - will PLC come back to the instruction SFC20-BLKMOV and contiunue copying, if it be interrupted by higher OB priority? I search almost everywhere and can not find information about it.
	Last edited by: SuHu at: 2/23/2018 7:36:24 AM
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2/23/2018 9:43 AM	Rate (1)
mopS04 Platinum Expert Joined: 3/5/2014 Last visit: 8/5/2022 Posts: 5521 Rating: (1058)	SuHu will PLC come back to the instruction SFC20-BLKMOV and contiunue copying, if it be interrupted by higher OB priority? I search almost everywhere and can not find information about it. hi SuHu, yes it will come back and finish the Block-Move. But the data that will be moved may not be consistent. The maybe changed during the interuption. hope this helps, regards,
	FCK WAR! Be nice!
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