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MEMORY CONCEPT DOUBT

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

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1/2/2015 6:59 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/13/2024 Posts: 5697 Rating: (715)	Hello, Because the actual values arewritten to the mmc in case of powerdown, at startup they are loaded again to work memory. Only in case of an older 300 ( with battery) you lose your data in case of low battery. 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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1/4/2015 11:07 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 12/18/2024 Posts: 711 Rating: (30)	Dear Mahesh, Can you please elaborate your question "Why the blocks are not initialised, like S7-400 with flash card without batteries" what is your doubt/ issue ?
	With Best Regards VIPZ
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1/23/2015 1:57 PM	Rate (0)
Mahesh N Bronze Member Joined: 10/3/2013 Last visit: 9/14/2024 Posts: 125 Rating: (3)	Mr. vipz In case of S7-300:- Retentive values & system data it is not initialize/reset with MMC on power down without Because when we download the blocks & system data, it is stored in MMC & then CPU fetch that data. In the case of power down the actual values of blocks are stored back into CPU & restored on warm restart when power up In Case of S7-400: Retentive values & system data it is initialize/reset with flash card on power down without batteries. I would just like to know why the phenomenon of S7-300 is not happening in case of S7- 400. Why it is initialized. Why the actual values of block are not stored back into the flash card. Regards, Mahesh Nakade

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1/23/2015 5:14 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/13/2024 Posts: 5697 Rating: (715)	Hello, Lets have a look at this picture: S7-400 memory concept You can see that user program is loaded to Ram Load Memory area. From Load Memoryrelevant parts are loaded to Work Memory (is also Ram) Ram memory needs power to retain it's contents. So without batteries, Ram is cleared and both Load and Work memory is cleared. In the (not the older CPU) 300, the MMC is the load memory, a MMC can retain the contents without power. In case of power down the data marked as retentive will be writen to the MMC, there is a super capacitor in the CPU that gives just enough time to do so.(not Always true i experienced) At power on these values are loaded again together with the user program. A 400 CPU can only write to Flash card in stop mode, so writing retentive data to Flash is not possible. In case of power down, flah cardand no batteries, the userprogram with the initial values are loaded to Ram again. Hope it's clear now, if not please return. Regards, Marcjan
	Last edited by: Marcjan at: 1/23/2015 5:21 PM Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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This contribution was helpful to 2 thankful Users vipz Yoran1997

1/27/2015 6:25 AM	Rate (0)
Mahesh N Bronze Member Joined: 10/3/2013 Last visit: 9/14/2024 Posts: 125 Rating: (3)	Hi, Thank you, In case S7-400:Ram is a Load Memory area. In case S7-300:MMC is a Load Memory area. Is there any special purpose to use RAM as a load memory area?

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3/30/2016 9:42 AM	Rate (0)
Wit_Moderator Moderator Joined: 8/21/2014 Last visit: 12/20/2024 Posts: 1041 Rating: (14)	New question published by IZ ALJABRE-JORDAN is split to a separate thread with the subject Changing the user program in RUN. Best regards The Helping Hand
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards Wit_Moderator
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