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MEMORY CONCEPT DOUBT

Created by: vipz at: 8/17/2013 11:50 AM (35 Replies)

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10/19/2013 6:18 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Marcjan, Sorry, i have attached second page of discusion.. Yes, i agree about your comment on older cpus. As per my understanding, all db are retentive and storing under mmc (during power down). But in this discussion ALL DB are NOT RETENTIVE its stating that all dbs are not retentive. Depends on internal cpu retentive memory, number of retentive dbs will vary. still can i conclude S7-300(new series) plc retentive values are store in MMC ?? regards
	With Best Regards VIPZ
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10/23/2013 8:59 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Hai, today i done some testing -- 1. made new program which include db and downloaded to 315 2pn/dp cpu. modified DB values via vat table. restarted the plc. showing values are retained. 2. turned off CPU, removed mmc and made power on. then again made power off, inserted the mmc and again power on. DB values are not retained. 3. repeated step2, after doing copy ram to rom operation. then values are retaining. so am correcting my last conclusion like this-- even in S7-300 / 400 the retentive values are storing internal memory of cpu only. regards vipz
	With Best Regards VIPZ
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10/23/2013 10:01 AM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, One thing is puzzling me now, how does the CPU keep these values in Ram without power? O.k. for a short period a super capacitor will do the job, did you try it for a longer period, let's say 1 day? It could be that the CPU detects that the MMC was removed en then loads the initial values. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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10/23/2013 11:54 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Hai Marcjan, What kind of testing you mean?? Is it like this way ?? set some value for db. then power off remove mmc keep as it is for minimum 1 day put back mmc give supply check value. correct?? regards vipz
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10/23/2013 2:25 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, You did this: 1. made new program which include db and downloaded to 315 2pn/dp cpu. modified DB values via vat table. restarted the plc. showing values are retained. Restart means power off and on again? Then leave power of for a longer period. See what happens then. Regards, Marcjan
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10/24/2013 8:14 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Hello Marcjan, 1. i have done test case as you mentioned -- DB value are retentive 2. test case as i posted -- DB values are retentive. .. then ??? regards vipz
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10/24/2013 11:03 AM	Rate (1)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, I have done some research myself Opened a CPU, there is a super capacitor of 1F, that will retain the values for a long time. I also found this: Retentivity of the data blocks: The main memory is not completely retentive for all CPUs. For some CPU types part of the main memory is retentive and the other part is non-retentive. Only the retentive part of the main memory can be used for retentive data blocks. That means that the CPU memory (main) is retentive for DB values, but i think not for ever because capacitor will be empty after some time. And this: If you wish to execute the STEP 7 function Copy RAM to ROM..., the current values of the process relevant data blocks in the load memory are overwritten with the current values from the main memory. If the process relevant data blocks are then transferred back to the main memory (e.g. after memory reset), then the new current values from the load memory are adopted by the CPU as initial values. In SIMATIC STEP 7 these new initial values are displayed in the “Actual value” column. Hope that clears e few things. Regards, Marcjan
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6/30/2014 1:11 PM	Rate (0)
CS Moderator Moderator Joined: 9/1/2005 Last visit: 10/4/2024 Posts: 4105 Rating: (195)	follow up question published byRSidis split to a seperate thread with the subjectconfused in S7300 memory. Best regards CS Moderator
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards CS Moderator
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12/18/2014 9:42 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4767 Rating: (123)	New question published byMahesh N is split to a separate thread with the subject S7-300 & S7-400, some doubt regarding memory concept. Best regards Min_Moderator

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1/2/2015 11:41 AM	Rate (0)
Mahesh N Bronze Member Joined: 10/3/2013 Last visit: 9/14/2024 Posts: 125 Rating: (3)	Dear All, It is all ok with S7-400. But what about the S7-300. It is working without batteries. Why the blocks are not initialised, like S7-400 with flash card without batteries.

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