S7-400 Retentive memory

Hi,

I would like to save some data after CPU shut down, so I  set first 32 memory bytes as retentive (screen attached). After that i move some data to memory MD and MW (in scope from 0 to 32), however after CPu shut down all data is lost. I have batteries assembled on CPU. What am I doing wrong? 

Best regards,
Lukasz

Hi,

Please see the FAQ below as it details possible retentivity cases on S7-400s:

Retentivity behavior of S7-400 CPUs and the CPU 318-2 CPUs

Although it is a bit old, I consider it quite complete. Does your installation and configuration meet the requirements for the data to be remnant after a power off/on?

Hi,

according to your link after cold restart all data is lost. Is it possible in S7-400 to save data even after cold restart? I have counter of working cycles and encoder preset value  - they need to be restored after shut down.

Best regards

Hello,

copy the values constantly to a DB and restore with the OB "StartUP" the values from the Data block to the counter and so on.

Scott