Keep variable, even when downloading new software. Any idea's?

Hello,

I have a program with runninghours functionality. Sometimes during testing we change/update the software. 

But only for the runninghour variables i want to keep them saved in the PLC or a MMC. 

Also want to keep the variable when the PLC has no powersupply. 

When to change the variable? Factory settings & when the PLC program changes the variable.

Can i do something with a special DB made for runninghours? And save it on MMC or something without it being erased when downloaded.

I hope someone has done this before. Maybe something with recipt or... whatever kind of solution. :) 

I just don't want to lose the hours which the machine is running. Because it's very important for maintenance. 

Which FW version do you have?

Consider using the RTM (run time meter) functionality.
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I use a CPU 1214C DC/DC/DC with Firmware version V4.0

I have taken a look at the RTM block. Few questions about it:

You still need to Save the value on the memory card with sending a "07" job to the block?

Without that the value is lost? Or is this an extra option for when u change the MMC?

Do you need an MMC ? And for these "jobs" you can send just a Job one CPU cycle?

There is no busy value which i can use to block sending a Job.

Tiaportalia

I use a CPU 1214C DC/DC/DC with Firmware version V4.0

I have taken a look at the RTM block. Few questions about it:

You still need to Save the value on the memory card with sending a "07" job to the block?

Without that the value is lost? Or is this an extra option for when u change the MMC?

Do you need an MMC ? And for these "jobs" you can send just a Job one CPU cycle?

There is no busy value which i can use to block sending a Job.

Saving onto an MMC is not a requirement..
but the advantage is when transfer the RTM to another CPU.
Saving onto an MMC can occur very infrequent.

Please see the highlighted sections of the attached PDF
(Extract from S7-1200 system manual).