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Actual data loss

Created by: KGI at: 10/22/2008 12:02 PM (9 Replies)

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10/22/2008 12:02 PM	Rate (0)
KGI Posts: 64 Rating: (0)	Siemens S7 configuration: - 6ES7 316-2AG00-0AB0 withmemorycard6ES7 951-0KG00-0AA0 and battery - OP27 - all the blocks are written on the EPROM Values are written from the OP27 to the S7-300 CPU. During a power failure of 3 seconds, the actual data of the datablocks in the CPU is lost. It looks like the inital values of the datablocks are written to the actual values again. How can we explain this, in other words how is the memory concept working of this configuration. I can not find a manual as an answer for this question... Regards, Kristof Gijbels Automation engineer Genzyme Flanders
KGI Posts: 64 Rating: (0)
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10/22/2008 1:52 PM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 7/31/2025 Posts: 9027 Rating: (1199)	Dear KGI, Have you seen this manual: http://support.automation.siemens.com/WW/view/en/8860591 See chapter 5, retentive datablocks. Is battery ok? Perhaps it's useful Best regards, Wizard

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10/23/2008 12:53 PM	Rate (0)
KGI Posts: 64 Rating: (0)	Is there a battery needed? For what reason?
KGI Posts: 64 Rating: (0)
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10/23/2008 1:31 PM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 7/31/2025 Posts: 9027 Rating: (1199)	Dear KGI, When you have no battery in CPU. After power failure, your programm and actual data will be lost. When power returns programm will be copied from FEprom. (using initial values of DB) So battery will save your programm and actual data in RAM, when there is a power loss. Best regards, Wizard

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10/23/2008 2:38 PM	Rate (0)
KGI Posts: 64 Rating: (0)	What's the difference between the EPROM that I used and the (new) MCC cards, for example S7 MICRO MEMORY CARD, 128KB (6ES7953-8LG11-0AA0)? Is the actual data saved in the MCC?
KGI Posts: 64 Rating: (0)
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10/23/2008 3:05 PM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 7/31/2025 Posts: 9027 Rating: (1199)	Dear KGI, The old S7-300 CPU's has integrated load memory. So Eprom is not needed and is only a back up of programm. When there is a power loss and the CPU has no battery or Battery is low, programm is lost. Only when you have Eprom, programm will be loaded when power comes up. The new S7-300 CPU's does not have integrated load memory, so MMC is necessary. They also have no battery, because when power loss, some data is written to MMC. That's the remenance memory and actual values of Datablock. Pay attention, sometimes not all Datablocks can save actual values. There is a limitation of memory that can be remanent. You can select which datablocks must save actual values. I hope this will help you. Best regards, Wizard

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10/23/2008 3:28 PM	Rate (0)
KGI Posts: 64 Rating: (0)	Thanks for you're answers Wizard, There still one question that I have: When I look online in the CPU, I see that all the blocks (datablocks included) are written in the EPROM. Now, when Inoticed this I assumed that the operating panel is writting the actual values to the EPROM and not to the actual values in the work memory. Apperently, when I analyse you're answers, the operating panel is writing the data in the datablocks that are in the work memory. So, the actual data of the datablocks in the EPROM is not updated at these moments. Only when I do a copy from RAM to ROM, the actual data from the datablocks in the work memory is copied to the EPROM. So I have to see it like this: old CPU's with EPROM: EPROM --> load memory --> work memory New CPU's with MMC: load memory (MMC) --> work memory Is this correct?
KGI Posts: 64 Rating: (0)
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10/23/2008 4:01 PM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 7/31/2025 Posts: 9027 Rating: (1199)	KGI There still one question that I have: When I look online in the CPU, I see that all the blocks (datablocks included) are written in the EPROM. Now, when Inoticed this I assumed that the operating panel is writting the actual values to the EPROM and not to the actual values in the work memory. Apperently, when I analyse you're answers, the operating panel is writing the data in the datablocks that are in the work memory. So, the actual data of the datablocks in the EPROM is not updated at these moments. Only when I do a copy from RAM to ROM, the actual data from the datablocks in the work memory is copied to the EPROM. So I have to see it like this: old CPU's with EPROM: EPROM --> load memory --> work memory New CPU's with MMC: load memory (MMC) --> work memory Is this correct? Dear KGI, When a panel is changing values, they are values in work memory. So it is not changed on Eprom. Yes you are correct about understanding Load memory and Work memory. Here is a link, which tells more about Copy Ram to Rom with different CPU's: http://support.automation.siemens.com/WW/view/en/15389520 Best regards, Wizard

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10/28/2008 3:11 PM	Rate (0)
KGI Posts: 64 Rating: (0)	When I remove the battery in the 6ES7316-2AG00-0AB0, and there are not blocks saved in the EPROM, and I cutt-off the power supply to the CPU, the blocks the are still in RAM when I power-up CPU again? I thought these blocks would be gone after the CPU was power less, with no battery back-up and no blocks in EPROM? Is the an internal battery? If yes, how long is this power supply valid?
KGI Posts: 64 Rating: (0)
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10/29/2008 1:13 PM	Rate (0)
JMJ Posts: 487 Rating: (45)	There is no internal battery for this CPU. But there can be some capacitors that stores the power for a short period. If you power outage is really short, the RAM may not have lost power by then. Tryturning of power for atleast30 seconds and see if it makes a difference. Also try after physcially removing theEPROM from CPU, there can be some program thatis on the EPROM that is being loaded when you restart the PLC.
JMJ Posts: 487 Rating: (45)
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