Finally found some time to get the code readout working. If someone's interested, here is the code
http://www.baedasui.de/downs/901.zip
There are two progs,
one for the 901, residing in the 0x300 segment ( sorry, a whole segment is to be cleared, so this one is lost forever ...) which outputs the content of the lower segs over a simple clocked serial protocol to the mcb900
and
one for the mcb itself which takes the stuff and sends it over the serial port to a pc.
Of course you have to set the boot vector of the ISPed lpc 901
http://www.baedasui.de/downs/901.zip
There are two progs,
one for the 901, residing in the 0x300 segment ( sorry, a whole segment is to be cleared, so this one is lost forever ...) which outputs the content of the lower segs over a simple clocked serial protocol to the mcb900
and
one for the mcb itself which takes the stuff and sends it over the serial port to a pc.
Of course you have to set the boot vector of the ISPed lpc 901