8/22/2013 12:41 PM | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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: 4/17/2024 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: 4/17/2024 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: 2/15/2024 Posts: 5697 Rating: (711) |
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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10/19/2013 6:18 AM | |
Joined: 9/2/2012 Last visit: 4/17/2024 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 |
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10/23/2013 8:59 AM | |
Joined: 9/2/2012 Last visit: 4/17/2024 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 |
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10/23/2013 10:01 AM | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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 |
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10/23/2013 11:54 AM | |
Joined: 9/2/2012 Last visit: 4/17/2024 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 | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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 | |
Joined: 9/2/2012 Last visit: 4/17/2024 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 | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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:
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:
Hope that clears e few things. Regards, Marcjan |
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6/30/2014 1:11 PM | |
Joined: 9/1/2005 Last visit: 3/5/2024 Posts: 4097 Rating: (193) |
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12/18/2014 9:42 AM | |
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1/2/2015 11:41 AM | |
Joined: 10/3/2013 Last visit: 10/26/2023 Posts: 123 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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1/2/2015 6:59 PM | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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
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1/4/2015 11:07 AM | |
Joined: 9/2/2012 Last visit: 4/17/2024 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 ?
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1/23/2015 1:57 PM | |
Joined: 10/3/2013 Last visit: 10/26/2023 Posts: 123 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 |
1/23/2015 5:14 PM | |
Joined: 4/22/2010 Last visit: 2/15/2024 Posts: 5697 Rating: (711) |
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 PMProblem solved? |
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1/27/2015 6:25 AM | |
Joined: 10/3/2013 Last visit: 10/26/2023 Posts: 123 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? |
3/30/2016 9:42 AM | |
Joined: 8/21/2014 Last visit: 4/17/2024 Posts: 946 Rating: (13) |
New question published by IZ ALJABRE-JORDAN is split to a separate thread with the subject Changing the user program in RUN. Best regards |
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