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Loose data when memory card change.

Created by: marocain at: 7/18/2012 3:35 PM (4 Replies)

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7/18/2012 3:35 PM	Rate (0)
marocain Posts: 3 Rating: (0)	Hello, I meet a problem with my plc. In fact, may application consists of several embded machines on the same box master (plc cpu314 + safety device ...) . When I change the embded machine I should change also the memory card (change the Plc program because the machine cycles are differents) all data saved on my Data bloc are lost ! It's more clear with an exemple: With the machinenumber 1I had scan barcod 123S2598D147J (stored in DB140)... after Iput outthe main box master (power supply = off) , I move machine number 1 and I replace it by the machine number 2 ... after that I put on the main box , I work with the machine number 2 ...Iput outthe main box master (power supply = off) , I move machine number2 and I replace it by the machine number1 ==> Result : In the DB140 IS EMPTY when the type is char and 0 when the type is a number ... !!! no data no barcod ... I don't understand what is the problem ... I notice that no program operation are handling may data in DB140 when I start the PLC ... Thank you for help...
marocain Posts: 3 Rating: (0)	Last edited by: marocain at: 7/18/2012 3:35 PM
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7/19/2012 10:51 AM	Rate (0)
miami Platinum Expert Joined: 8/31/2005 Last visit: 8/20/2024 Posts: 2198 Rating: (328)	The MMC holds only the initial values of a DB. The actual values are only in the working memory. You can stop the CPU and perform a "RAM to ROM" to copy the actual values to the MMC or use SFC 84 "WRIT_DBL". When a MMC is changed the CPU makes a reset. This deletesthe data in the working memory and loads the program (including the DBs) from the MMC. Use RAM to ROM or the SFC84 to update the MMC before youremove it fromthe CPU. The data in a DB may change every cycle, but the MMC has a limited numbers of witing, so the actual values can not be stored on the MMC. The RAM of the working memory can do this. Beware of calling SFC84 to often, e.g. in OB1. This will quickly bring the MMC to it maximal writing possibilities.

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7/19/2012 3:12 PM	Rate (0)
marocain Posts: 3 Rating: (0)	Thank you for help... Now I understand the origin of my problem .... How many times that I can write on a MMC ? it is specified in documentation ? So, I want call SFC84 only when the power is turning off ! There are some OB availables called on this event (power off) ? my be I am a big dreamer but hope is nice : -) .....
marocain Posts: 3 Rating: (0)
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7/19/2012 5:47 PM	Rate (0)
miami Platinum Expert Joined: 8/31/2005 Last visit: 8/20/2024 Posts: 2198 Rating: (328)	marocain How many times that I can write on a MMC ? it is specified in documentation ? So, I want call SFC84 only when the power is turning off ! There are some OB availables called on this event (power off) ? my be I am a big dreamer but hope is nice : -) ..... No, ther is no OB started, when the power is switched off. This FAQsays: "The memory blocks of the MMC memory permit at least 100,000 write/delete operations." And when you read this FAQ: Yes, at power off the data of DBs is stored on the MMC, due the RAM will loose it. During the next startup, if the MMC wasn't changed, this data is restored to the RAM. But the way the data is stored on the MMC is different to the way than the user program is stored.

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7/20/2012 10:53 AM	Rate (0)
marocain Posts: 3 Rating: (0)	Ok , It's clear for me now ... There is no event allows me to call SFC84 before turning off the machine .... but may be I will creat an event by pressing a touch on the OP73 .... Thanks.
marocain Posts: 3 Rating: (0)
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