Hi all,

Does anyone still know the MC68701? It's the EPROM version of the 6801.
It offers a Mode 0 which allows for reading and writing the internal
EPROM - not like the Hitachi 68xx which can be read and written as 27256
with an appropriate adaptor, this beast needs a monitor program run in
mode 0 to work on the EPROM.

Now I have one 68701 left with some special code in it and need to
reverse engineer the serial protocol it talks (there are some codes sent
to another system which couldn't be simulated once we tried, so I need
to know which condition leads to sending them).

I built a small circuit with the 68701, a HCT573 latch, a 2764 with
Motorolas ProBug monitor in it and a HCT138 wired somewhat weird - A12,
A14 and A15 go to A,B and C, while A13 goes to /G1, /G2 is grounded and
G3 goes to E. Which makes a chip select for B000:BFFF on Y7.
But I cannot get the damn thing reading from my EPROM! The data sheet
says clearly that in mode 0, the reset vector is BFFE:BFFF. But my 68701
will never read from any Bxxx addresses for a single cycle!
Switchhing it to mode 2 or 4 for example works. Opposite to the 6801,
which fetches the reset address from FFFE:FFFF also in mode 0 (but then
allowing those two addresses to be supplied externally for 2 E-cycles)
the 68701 should read from my EPROM on Bxxx.

Anyone an idea?