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MEMORY CONCEPT DOUBT

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

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8/23/2013 8:04 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Marcjan, very sorry for my bad understanding... 2. if am using plc without load memory, but providing buffer battery, retentivity will happen ?? i mean without external cards *yes if you have backup battery the Retentivity will last as long as your battery is o.k.. thats the case retentive memory is inside cpu memory or inside card or collective memory ?? 3. if am using FLASH card without battery backup, retentivity will work ?? No. after power on the program is loaded from flash to work memory, all data blocks will use initial values. my understanding-- if we want retentivity, we should use battery backup. even the card is RAM or FLASH. please guide thank you vipz
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8/23/2013 8:10 AM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, The S7-400 has always a load memory, internal or when card is used internal and external. Yes to have retentivity you need a battery. Also if you have Ram-card. If you have no battery and no Flash card the PLC will be empty after powerdown. The 300 (with the small MMC card) writes the retentive values to the card at powerdown, the 400 does not! Regards, Marcjan
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8/23/2013 8:50 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Marcjan, now almost clear.. The 300 (with the small MMC card) writes the retentive values to the card at powerdown -- ok the 400 does not! -- means ?? retentive is only internal memory ????? regards vipz
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8/23/2013 9:58 AM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, Hope this makes it all clear: QUESTION: Is the status of an S7-400 CPU after power off/on (without back-up battery) the same as the state after an overall reset? ANSWER: In the case of power failure or an overall reset (MRES) in non-back-up mode the following memory areas of the S7-400-CPU are reset: Dynamic load memory (RAM) Main memory System memory All the data that is stored in these areas is lost with the exception of the MPI parameters (e.g. MPI address of the CPU). These remain after a power failure. Thus, in both cases the CPU behaves identically, which means that after a power failure or an overall reset, the CPU still remains able to communicate. After power failure, the only way of starting is a Restart. Important: In non-back-up mode there are no remanent memory areas. Regards, Marcjan
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8/23/2013 11:04 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Marcjan, so can i conclude like this ?? 1. in S7 300 series plc, retentive memory is inside mmc, retentive data will get write in to MMC at the time of power down. 2. in S7 400 series plc, battery is must for retentive datas. 3. If RAM card, battery backup for user program and retentive datas.(400 series) 4. If flash card, battery backup only for data retentivity. user program is safe inside flash card. 5. If using flash card without battery, datas are not retentive. 6. in S7 400 series plc, retentive memory is not inside the external RAM/FLASH card, its in internal load memory of the CPU. 7. Battery will give the backup to RAM card and internal load memory. thanks vipz
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8/23/2013 5:10 PM	Rate (1)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, Yes, you got it right in big lines, some terms you use mix up a little but that could be a language problem. Glad we could help you to understand this not so easy memory concept of the 400 system. Have a nice weekend. Regards, Marcjan.
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This contribution was helpful to 2 thankful Users manmeet vipz

8/23/2013 5:25 PM	Rate (1)
manmeet Gold Member Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71)	Just a handy chart .............................. [img]/tf/WW/en/postattachments/download?attachmentId=39599[/img] Attachment S7_MEMORY.jpg (499 Downloads)

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This contribution was helpful to 2 thankful Users Marcjan vipz

8/23/2013 5:50 PM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Both, realy nice work.. you guys helped me to understand memory concept properly.. regards vipz
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This contribution was helpful to 2 thankful Users manmeet Marcjan

10/18/2013 7:08 PM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30)	Dear Both, see some discussion about retentive memory area-- stating that s7-300 retentive area also in plc internal memory. so our conclusion is wrong ?????? please see link.. DB- retentive cases regards vipz
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10/18/2013 8:35 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, Your linkin is like a perpetium mobile It brings me back here and then back again to the link. Before i get a mouse arm, let me tell you this: There are 2 types of S7-300 PLC's. The older type with backup batteryand a memory concept (almost)simular to the s7-400. The new ones without battery and a MMC. I think that's why you got lost in the s7-300 memory concept. Regards, Marcjan
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This contribution was helpful to 1 thankful Users olloy

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