Erasing the contains of the DS1225 doesn't make sense, this IC holds setup information like bootselections. The only thing I could do to get the clock to a legal value is by reprogramming the DS12887A chip. Maybe this is possible by placing this chip in a Pentium PC and reprogram it, but I hadn't one.

What I did was (the story):

Place this IC in a 'bread-board'. Connect Vcc, GND to a 5V power supply. Pull every input pin of the chip to +5V with 47k resistors. Reset it by connect pin 18 to GND. Erase contents of user RAM by connecting pin 21 to GND for a few seconds. Now user RAM is erased, but not the time/date data. I did this by exactly following the fetched data-sheet from DALLAS (www.dalsemi.com).

First program the B register to get the 'SET' bit to '1'. This makes permission to modify the time registers possible. Now program all 10 date/time registers with legal BCD values. At the latest program the B register again with the 'SET' bit to '0', also set the 'DM' bit to '0' this indicates BCD values in the date/time registers.

This was all done by following the write timing information of the data sheet. A '0' is made by connect a pin to GND with a wire. A '1' is made by connect to nothing (because of the 47k pull up resistor).

After two tries the date was somewhere in 1980 (I made some mistakes I think). Now modifying date/time was possible in the setup screen. I had luck!

If this won't work I had to buy a new chip I think...