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S7 - 315 2DP losing Datablock setpoints

Created by: abproj at: 9/8/2008 9:09 AM (10 Replies)

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9/8/2008 9:09 AM	Rate (0)
abproj Posts: 58 Rating: (1)	I have a S7 315 2DP (6ES73152AG100AB0) on a remote site where they keep losing analog setpoints that are stored in datablocks. These are for analog alarm setpoints, PID setpoints and other general analog values. We suspect the power is going off and the UPS supplying the power is faulty. I download lots of PLC information on the restarts: 1. It seems this PLC only has OB100 - warm restart 2. Warm Restart : In this restarts your memory areas values remains same i mean what ever the values of memory areas as well as data blocks in retentive area will remain same or regained if u have battery back up. This PLC has a micro memory card - it should never lose its setpoints, but they seem to be getting the initial datablock values. Why would it default to the origional values if you can only do a warm restart? How can we prevent this loss of setpoint data from happening?
abproj Posts: 58 Rating: (1)
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9/8/2008 9:29 AM	Rate (0)
aikona Posts: 487 Rating: (36)	HI Not sure if this will help but ... don't you have to do a ' Copy RAM to ROM ' to keep your values bye Eric
aikona Posts: 487 Rating: (36)
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9/8/2008 9:59 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 9/29/2023 Posts: 8593 Rating: (1132)	Hello abproj, Please have a look at manual: http://support.automation.siemens.com/WW/view/en/12996906 See chapter 4.1.2. Perhaps it helps. Best regards, Wizard

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9/8/2008 11:22 AM	Rate (0)
abproj Posts: 58 Rating: (1)	Thank you for that manual - it contains the info I was looking for. 1. Thanks for this: Promming (RAM to ROM) When writing the RAM content to ROM, the actual values of the DBs are transferred from RAM to load memory to form the start values for the DBs. 2. From the manual: ----------------------------- Restart (warm start) ● All retentive DBs retain their actual value (non-retentive DBs are also supported by CPUs with firmware >= V2.0.12. Non-retentive DBs receive their initial values). Retentive behavior of a DB for CPUs with firmware < V2.0.12 For these CPUs, the contents of the DBs are always retentive at POWER ON/OFF or STOPRUN. Retentive behavior of a DB for CPUs with firmware >= V2.0.12 These CPUs support the generation of data blocks with "NON-Retain" (not retentive) property. < not sure what the firmware version is > Retentive data in load memory Your program in load memory is always retentive: It is stored on the SIMATIC Micro Memory Card, where it is protected against power failure or CPU memory restart Retentive data in work memory Therefore, the contents of retentive DBs are always retentive at restart and POWER ON/OFF. Data blocks assigned the "NON-Retain" property are initialized with their start values when power is cycled off and on and and when the CPU goes from STOP to RUN. -------------------------------- These DB are not set as "NON-Retain", therefore from the above they should never default to the initial values. Could the CPU be defective?
abproj Posts: 58 Rating: (1)
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9/8/2008 11:39 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 9/29/2023 Posts: 8593 Rating: (1132)	Hi, Perhaps you want to retain too much data The CPU can retain 128 Kb Length of the non-volatile work memory for retentive data blocks Please have a look, there might be DB's you do not have to retain. Best regards, Wizard

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9/8/2008 11:52 AM	Rate (0)
abproj Posts: 58 Rating: (1)	Thank you, My total program is 66700 bytes and the DB's are 12500 bytes. There are DB's that do not need to be retentive. (the site is about 6 hours driving away) If you mark some DB's as non retentive - are they loaded differently to retentive DB's? Regards
abproj Posts: 58 Rating: (1)
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9/8/2008 12:30 PM	Rate (1)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 9/29/2023 Posts: 8593 Rating: (1132)	Hi, There is no difference of loading DB. The non-retentive DB's will loose actual values and use Initial values. What is length of DB's? Best regards, Wizard

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9/8/2008 12:43 PM	Rate (0)
abproj Posts: 58 Rating: (1)	Hi, There is about 140 DB's, mostly instance DB's of about 66 bytes about 30 DB for data and setpoints, mostly about 80 bytes. The biggest is 254 bytes and goes up to byte no 218.
abproj Posts: 58 Rating: (1)
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9/8/2008 1:38 PM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 9/29/2023 Posts: 8593 Rating: (1132)	Hmmm, All DB's start with initial values? Do you have other remanent data (MW, timers etc.) Do they have actual data? Just wondering: How big is MMC? Best regards, Wizard

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9/8/2008 1:55 PM	Rate (0)
abproj Posts: 58 Rating: (1)	Hi, The MMC is 128 kb. I am not sure that all the data goes back to origional values - the information is being relayed from site by a mech engineer. From what he described it would seem like most of the SP date. Thanks for all the information.
abproj Posts: 58 Rating: (1)
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