S7 400 and 300 Backup actual values

Jim.M · Feb 5, 2015

Hi, Ive been working on a backup program for my PLCs. I have tried the SFC 84 and SFC83 blocks to backup the actual values on my CPU3xx´s

But how do you guys solve this with a CPU4xx? There is no MMC card there?

My goal is to backup actual values because ive had som problems with powerlosses etc. And if the battry in PLC dies the actual values in DBs seem to dissapear?..

Anyone with experience from this?

wimpiesplc · Feb 5, 2015

As far as I know, PLC which use MMC card don't have a battery and according to this link https://support.automation.siemens....csview&extranet=standard&viewreg=WW#A15423286:

In the case of CPU modules that work with a micro memory card (MMC) the load memory is on the MMC. When loaded, the program is stored on the MMC in such a way as to be immune to power failure and overall reset. The program is therefore always remanent in the load memory (on the MMC).

Jim.M · Feb 5, 2015

wimpiesplc said:
As far as I know, PLC which use MMC card don't have a battery and according to this link https://support.automation.siemens....csview&extranet=standard&viewreg=WW#A15423286:

Ok thats interesting.. Therefore one nedd to backup all actual values to MMC in case of power failure. But if I have a CPU 400 do I have battery then?.. Im gonna check my CPU´s.

JesperMP · Feb 5, 2015

In S7-400, the backup battery should keep the actual values.
You can use OB81 to generate an alarm if the battery is dead.

Jim.M · Feb 5, 2015

JesperMP said:
In S7-400, the backup battery should keep the actual values.
You can use OB81 to generate an alarm if the battery is dead.

Hmm Thats pretty smart.. But is there any way to backup actual values in 400 like we do in 300?

JesperMP · Feb 5, 2015

Not that I know of.

Jim.M · Feb 5, 2015

JesperMP said:
Not that I know of.

Thanks anyway I found some example code for OB81 that i can use.

https://support.automation.siemens....slib.csinfo&lang=en&objid=7701820&caller=view

S7 400 and 300 Backup actual values

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