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Issues when setting data retentive

Created by: rico100 at: 8/3/2011 12:55 PM (4 Replies)

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8/3/2011 12:55 PM	Rate (0)
rico100 Experienced Member Joined: 10/14/2010 Last visit: 1/3/2025 Posts: 59 Rating: (3)	Hi all, I've been working on an FB that will be used to totalise the amount of product in each bay. The FB works fine, however when I make certain areas of my static data retentive I get some strange values appear in the data I've set retentive? I've scratched my head over this issue for a few hours now and wondered whether any of you gurus out there could have a look at the block and see if you can see any issues with it please? I think it may have something to do with the MUX instruction? If you'd like a copy of the project let me know and I'll email it. Thanks Rich Edit: I'm using TIA V11 Update 2 PLC CPU 1214C firmware V2.03 Attachment Total.pdf (733 Downloads)
	Last edited by: rico100 at: 8/3/2011 1:05 PM
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8/3/2011 1:22 PM	Rate (0)
bakerjw Posts: 126 Rating: (18)	What version of TIA portal are you using and what is the firmware version of the PLC? I didn't see anything out of the ordinary in the function block but wonder why you are moving retentive data to a temp location and then back at the end of the processing. In the S7-1200 retentive areas are the same type of storage as non retentive areas. They are just marked as retentive. When the PLC detects a power down condition then the retentive area is copied into flash memory. PM incoming. John
bakerjw Posts: 126 Rating: (18)
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8/3/2011 1:32 PM	Rate (0)
rico100 Experienced Member Joined: 10/14/2010 Last visit: 1/3/2025 Posts: 59 Rating: (3)	Thanks for looking, I'm using I'm using TIA V11 Update 2 PLC CPU 1214C firmware V2.03 Moving the data to the temp area was an attempt to fix the issue. Didn't think it would make a difference but was running out of ideas. Cheers I

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8/3/2011 3:58 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/21/2025 Posts: 15549 Rating: (2465)	Does your function block complete all tasks in a single scan? Do you call the function block more than once per scan? I've seen odd things with DBs associated with FBs. I would "fix" them by creating global DBs with retentive features, and access them inside the FBs. If that "fix"es the probem you are seeing, your function block is likely in need of a change. I found using global DBs and FCs reduced these kinds of problems. Maybe one of these days I'll know S7 and Siemens PLCs well enough to get FBs to behave, though it is likely my problem trying to solve a problem using the wrong tool.
	science guy
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8/4/2011 9:19 PM	Rate (0)
rico100 Experienced Member Joined: 10/14/2010 Last visit: 1/3/2025 Posts: 59 Rating: (3)	Installed SP1 today and the problem has gone away I'm pretty sure it had something to do with MUX instruction, because if I but i used the kwh_init in the first network I didn't get weird values in it. This was the main reason I moved my retentive data to temp variables in the hope it would solve the issue when i moved kwh_init back to the network between the MUX instructions.But it didn't. Be nice to know if the was an issue and I didn't have a dodgy installation that didn't compile the program correctly? Thanks

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