Siemens S7-312C retentive memory

[Pego]

A client asked me to modify an existing system.
It is a Siemens S7-312C compact CPU and a OP3 text display.
Now the bitmemory MB0 to MB 60 is used to store variables that can be changed via the display.
But this range is far too small for the variables I want to store, so I want to use DB1 for this.
In the hardware configuration->properties->Retentive Memory I can not select any DB however....
Are the DB's automaticaly saved when the CPU powers-down?
I can not imagine that the 128 bytes of bitmemory is all that can be used to store data.....
Just want to be shure before I tell my client things I can not realize.
I hope somebody can tell if I can use DB1 for this or not.
PG

 

[RMA]

I don't have the manuals at home and I'm not going to be in the office for the next few days, while I don't know the 312, I'm pretty sure that in all the modern MMC based 300 CPUs the DBs are retentive.

You should get confirmation from our resident S7 gurus before lunch!

 

[PLucas]

I believe all DB's will be retentive unless specified (I might be wrong on that), or maybe just up to DB511

Right click a DB block and select properties, then select the 'general part 2' tab and check to see if the 'non-retain' box is unchecked.

The picture below might help

Paul

 

[ivo.maenen]

DB's are retentive on the MMC voor the S7-312c