I wouldnt get in to the habit of removing the MMC with the power on.
While I agree it's probably not a good idea to get into this habit, in fact, there is no problem for the MMC card as such in removing it with power on (apart from the original problems with retentive memory), however there is a VERY big problem removing the card with the CPU running. If the CPU happens to be writing to the card when it is removed, you can finish up damaging the format of the MMC. If that happens you have no other choice than to send the MMC back to Siemens for reforming.
By the way, a word of warning to anybody meeting the MMC cards for the first time - the MMC is formatted with a proprietary Siemens format - DO NOT TRY AND FORMAT THE CARD BY PUTTING IT IN A NORMAL CARD SLOT IN A PC - if you do you'll find yourself in the same situation as described above and have to send the card back to Siemens for repair.
BTW2, the newest generation of MMCs appear to have an "improved" encryption system for the format which results in older CPUs not being able to work with them without a Firmware upgrade.
They also appear to be a bit unreliable at present - I recently wasted a couple of days, when I used a new 4MB MMC to upgrade the firmware of my 317 CPU (which had a few bugs, which together cost be nearly a week of wasted time bonkhead ) - the upgrade went through with no problem, but I then couldn't get the program to download to the MMC. I spent the best part of two days trying everything possible out - download from PG, download over the network, write the program directly with a prommer - all to no avail. Then I phoned the hotline, who listened to my description of the problem for all of ten seconds, before interrupting to say "No problem the MMC's faulty, send it back and we'll send you a new one."! banghead
So don't forget, just because you can download the firmware upgrade and write it to the MMC with the Prommer, then put the MMC in the CPU and update the Firmwaare with no problems - IT DOES NOT MEAN THE MMC WILL RUN CORRECTLY WITH S7!
Edit: Just saw your bit Jesper,
If you remove the MMC with the CPU powered up, as soon as you remove the MMC (even with the program not running) the STOP lamp goes into slow blink and you cannot restart the CPU without doing a memory reset.
Because I assumed this memory reset only reset the CPU memory (I'm pretty sure I remember reading somewhere in the manuals that memory reset does NOT clear (anything in -
my interpretation!) the MMC), I thought that if I left the CPU in stop after the memory reset and then switched the power off, then set the CPU switch to RUN and then switched the power back on, the CPU would do a normal power recovery and fetch the rententive memory values from the MMC, which I assumed would not have been changed, since the CPU HAD NOT RUN since the memory reset.
However when I tried it the DM- and M- values were again zero.
All my initial values were non-zero and in no case did I ever get the initial value. Either I got the value stored at run time. I'm pretty sure the only time you'll get the initial value back is if you download the original program again from the PG/PC.
If anybody has any specific ideas they'd like to try out, let me know the 314's still sitting around doing nothing, just like me!