8/22/2013 12:41 PM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715) |
Hello,. Please don't mix up MMC (for 300 CPU) and Flash/Ram- cards. How can I get an overview of the S7-400 memory concept? This FAQ, will answer most of your questions, if still in doubt about any part of this FAQ, please return. Regards, Marcjan |
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8/22/2013 1:49 PM | |
Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71) |
Yes MMC
Yes
You don't hace access to PLC internal memory (Working memory). You have access to only Load memory. So everything is stored in Load Memory. Work memory can't be increased where as Load memory can be increased using (MMC, RAM, EPROM) In 400 there are two kinds of Load Memory
There is no MMC here ! In a given 400 system you can either use RAM or EPROM in a given slot of CPU. If RAM is used no special method required to save program but in case of EPROM you have to choose "Load user program to memory card" option. RAM needs battery to save your program while EPROM does not requires it. Always think Load Memory as hard disk of your PC, and Work Memory as RAM of PC. Programs are saved in Hard Drive (Load Memory) and OS decide how much of RAM (Work Memory) is to be alloted when it is made to run. Now if you program is so big that it required more RAM(Work Memory) then installed capacity, you have to buy a PC (PLC) with more RAM (Work Memory) ! Simple ! Regards, Manmeet. |
Last edited by: manmeet at: 8/22/2013 1:54 PM |
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8/22/2013 6:31 PM | |
Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30) |
Dear Manmeet, thank you for the reply.. I agree.. regarding, ·If my program size is greater than internal memory of CPU, am using FLASH card. And using normal download option, will it get download properly? ** ?? In the case of backup batteries(400 system), is it giving backup supply to PLC Internal memory also ( I mean to both the RAM card and PLC internal mem) ? ** ?? regards vipz |
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8/22/2013 6:59 PM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715) |
Hello, 1st : if the program is bigger than the load memory it will not be downloaded correctly. 2nd: yes battery supplies both cpu ram and external ram-card. Regards, Marcjan
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8/22/2013 7:10 PM | |
Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30) |
Dear Both, in s7 400 also, retentive memory is inside RAM/FLASH card ?? in s7 400, we can use plc without LOAD MEMORY (WITHOUT RAM,FLASH CARD) provided program size is small . correct ? in that case retentivity will work if am providing buffer battery ?? regards vipz
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8/23/2013 6:10 AM | |
Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71) |
Yes
Your prgram goes in Load Memory and you need it for any downloaing to take place. You can just do some configuration changes in hardware to optimize the usage of work memory.
Yes Also follwong are few lines which I have taken from Simatic Manager Help. Just copy paste "Retentive Memory Areas on S7-400 CPUs" for more details.
Regards Manmeet |
Last edited by: manmeet at: 8/23/2013 6:11 AM |
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8/23/2013 7:21 AM | |
Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30) |
Deat Manmeet, some points are not clear to me.. 1. in s7 400 can we use PLC without any load memory?? consider my test program is very small compared to plc memory. 2. if am using plc without load memory, but providing buffer battery, retentivity will happen ?? 3. if am using FLASH card without battery backup, retentivity will work ?? regards vipz
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8/23/2013 7:42 AM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715) |
Hello, 1. Load memory of the 400 system is the Internal Ram or External Ramcard/Flash, picture From the load memory the programblocks are loaded into the (internal) Work memory. 2. yes if you have backup battery the Retentivity will last as long as your battery is o.k.. 3. No. after power on the program is loaded from flash to work memory, all data blocks will use initial values. Without battery the work memory and the internal Ram is cleared. Regards, Marcjan |
Last edited by: Marcjan at: 8/23/2013 7:43 AMProblem solved? |
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8/23/2013 8:04 AM | |
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 | |
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 | |
Joined: 9/2/2012 Last visit: 8/15/2024 Posts: 711 Rating: (30) |
Dear Marcjan, now almost clear.. the 400 does not! -- means ?? retentive is only internal memory ????? regards vipz
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8/23/2013 9:58 AM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715) |
Hello, Hope this makes it all clear:
Regards, Marcjan |
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8/23/2013 11:04 AM | |
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 | |
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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8/23/2013 5:25 PM | |
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]
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8/23/2013 5:50 PM | |
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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10/18/2013 7:08 PM | |
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 | |
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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