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10/6/2009 4:22 PM | |
Joined: 4/24/2006 Last visit: 9/20/2024 Posts: 8742 Rating: (1168) |
Dear Waqas, Please have a look at this link: http://support.automation.siemens.com/WW/view/en/431638 And here is manual: http://support.automation.siemens.com/WW/view/en/1109582 See page 36. Hope it will help. Best regards, Wizard |
10/6/2009 4:33 PM | |
Joined: 5/28/2008 Last visit: 9/11/2024 Posts: 1343 Rating: (141) |
Hi, values in datablock are fix and will be read-in at every restart of CPU. You can change them during runtime, but don't save them after power off. You have to save your values in retentive memory and write them back to e.g. VW104 on start-up. To adjust your retentive ranges, have a look to system block. There you can enter ranges to use. But retentive memory will be erased, if capacitor is broken or "empty". Then you cann use S7-200 EEPROM to save values or memory cartridge. Have a look at these FAQ's: How do you perform non-volatile saving of changed parameter data as variable ranges in the CPU's internal EEPROM memory? Duration of the Retentive Feature in S7-21x and S7-22x Retentive data area of the S7-21x Remanent data areas of the S7-22x In manual yo find further information about retentive memory and save values in EEPROM (SMB31) regards |
10/6/2009 4:38 PM | |
Posts: 2930 Rating: (432)
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Hi, S7-200 memory basics: If you add values in DB and you download it to PLC then an internel EEPROM will be written with the value of your DB and it will also be copied to the RAM the PLC is working with. If you write a differnet value via user program using a MOVx instruction then inside the PLC you have two different values. DB1 VW200 is in EEPROM, the value you have downloaded with MW VW200 in RAM written with the MOVx instruction. By default VW in RAM is retentive. So as long you change nothing and the internet SuperCap can spend power and you do a power cycle, you will have the two values at the same VW location (EEPROB and RAM). What you want to do is to protect the latest modification and have it available independant how long the power of the PLC is OFF. You can use SMB31 & SMW32 to copy from RAM -> DB (avaialbe for unlimited time), or Some HMI's offer to copy complete RAM -> DB, or You can use MW to create a DB from RAM of you can download a library to copy memory areas from RAM -> DB I think for you the library is the best. You get it from www.s7-200.net free of charge. What you need to do is if you change a value from your panel then you normaly get a bit. Use this bit to copy the chaged value from RAM -> DB. Thats all. Sorry the long answere but you should know how to deal with S7-200 memory ranges. regards |
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