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Is flash memory any use for 414-H redundant PLC when modifying program a lot?

6/8/2010 8:42 PM	Rate (0)
Hewking Posts: 14 Rating: (0)	Hi Everybody I've got 2 Hot/Standby PLC's (414-4HM14-0AB0) with 2 Mb flash cards. When modifying program and downloading to PLC by using button from the menu - RAM memory will eventually be used at 100 % and compressing will not help any more - the only way would be downloading through command "download user program to memory card" which will free RAM memory but is possible in STOP mode only. During bench-testing I did a test and noticed that after using command "Download user program to memory card" to HOT PLC it couldn't start (because flash memory in HOT PLC was different to flash memory in Standby PLC). To make both PLC's synchronized again I had to download program to Standby PLC using command "Download user program to memory card". Only then both PLC's synchronized and were running together but both PLC's had to be stopped for about 2-3 minutes to carry out that procedure. I wonder if there is any way out of that problem so both HOT/Standby PLC don't have to be stopped at the same time- are flash cards any use for H series PLC's when there is need to modify program a lot on site or only RAM cards would be useful? Please help. Thank you.
Hewking Posts: 14 Rating: (0)
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6/10/2010 3:42 AM	Rate (1)
H-H Platinum Member Joined: 7/2/2008 Last visit: 12/21/2025 Posts: 929 Rating: (309)	Hello Hewking, When I look at S7-400H manual (Page 55) I read the following: What type of memory card should I use? want to be able to edit your program in RUN mode, use a RAM card. I prefer to use the RAMs with S7-400 however, I think you can modify the user program in flash memory cards of an H-System but I think you will have take out synchronization cables while downloading to both CPUs. I think in this case The CPUs will not be able to check user program in each other. 1- Disconnect Synch. cables. 2- Download user program to reserve CPU (B)and put it in RUN. Now both CPUs are supposed to be in RUN mode however the IM153-2 still listens to the CPU with original user program. 3- Put your original master CPU (A) in STOP. The IM153-2 should be switched to CPU B with modified program. 4- Download user program to CPU A. 5- Connect synch. cables again. 6- Put CPU A in RUN again. As I told you I never tested it but I think it may work this way and I hope you can test it on your test bench and tell us the results . I still recommend to replace your FLASHs with RAMs. Best regards. H-H

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This contribution was helpful to 1 thankful Users Hewking

6/14/2010 2:30 PM	Rate (0)
Hewking Posts: 14 Rating: (0)	I test it today and it works! Thank you very very much.
Hewking Posts: 14 Rating: (0)
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This contribution was helpful to 1 thankful Users H-H

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