S7 "maintenancefree" MMC card.

Hi.

A customer of mine has experienced a problem to which I cannot explain the cause.
One possible cause could be that the retentive data on the MMC card has been lost somehow. Or the data from RAM has never been written to the MMC card.

According to Siemens, the data from RAM shall be written to the card at every power off. In this way the data is retained even without battery backup.

My question:
Has anyone ever experienced that an MMC failed to retain the data as intended ?

No but I have heard tell of this when I customer treats this like an SD card and "hot draws" it . They don't like that....
And like everything - of course they never do it

It happens to me a few times. Sometimes CPU starts up with values saved during previous power down, sometimes with initial values :-(. Only solution to this is to copy DB blocks to S7 project and then write them back to the PLC then everything works OK.
I think that there may be a problem with voltage monitor in S7-300 MMC CPU's.

gregoryg said:

It happens to me a few times. Sometimes CPU starts up with values saved during previous power down, sometimes with initial values :-(. Only solution to this is to copy DB blocks to S7 project and then write them back to the PLC then everything works OK.
I think that there may be a problem with voltage monitor in S7-300 MMC CPU's.

Click to expand...

Hi, I have same probrom like JesperMP and i think chang the initial value of datablock is a good idea. However, it is not a good thing to chang initial value one by one....Anyone have EZ way to 'copy Act. value to Init. value'?
Thanks

Anyone have EZ way to 'copy Act. value to Init. value'?

Click to expand...

In Simatic Manager: PLC -> Copy RAM to ROM

I'm not absolutely sure, but I believe this copies all the DBs, not just one that is marked. This means that if you have any DBs where the Initial values are intentionally different from normal running values (for initial start-up), then these may be overwritten as well!

The other way, if not too many values are concerned, is to create a new DB and copy the contents of the original DB into the new one. Then edit the Initial values to what you want and then (not before!) save the new DB. Then delete the original DB and rename the new DB to the original name and download it to the PLC.

Unfortunately I dont think copy RAM to ROM achieves that.
I did post a method eons ago, which involved generating the source, then manipulating the source in Excel, and then generating the DB with the modified source. But it is quite tedious.

s7xp has a comercial tool to copy the actual to initial values in one go: www.s7xp.com

JesperMP said:

Unfortunately I dont think copy RAM to ROM achieves that.
I did post a method eons ago, which involved generating the source, then manipulating the source in Excel, and then generating the DB with the modified source. But it is quite tedious.

s7xp has a comercial tool to copy the actual to initial values in one go: www.s7xp.com

Click to expand...

trying to find stxp but the website is down, does it still exist?

If you go to Runmode.com, under Useful stuff you will find a freeware tool to read and write the MMC card.

dahnuguy said:

trying to find stxp but the website is down, does it still exist?

Click to expand...

S7XP. The link in the quote leads to the site. But I have to admit it looks unattended.


You can also send a PM to forum member s7xp.com.