22 Dec
2005
22 Dec
'05
3:03 p.m.
Other (related) things that I am looking for....
1) The plastic ROM carriers. These are plastic mouldings that you put a
DIP-packaged EPROM into, then crimp the pins over. The same carriers were
used in the Tandy M100, and I think 24-pin versions were used in that
Panasonic hand-held machine that gets mentioned here. I need the 28 pin
ones, I think Molex once made them.
Don't have any spares unfortunately - but FWIW, I believe it is possible to insert
ROMs without them (not great, but possible). I believe I have seen a reference to
this somewhere on the web.
2) Is the PX4 technical manual on the net anywhere
(I've found the PX8
one already). The thing I need most at the moment is the pinout of the
cartridge connector. I have a 3rd party 512K (!) RAMdisk module there
which doesn't seem to work.
I'd be interested in any of this info as well.
The ROM sits in the second half of the address space
(it's an 8K ROM,
27C64, and it's enabled when A15 is high. It's ghosted 4 times). If this
is like a 68xx, I would expect vectors at the very top of the address
space, with the highest one of all to be the reset vector MSB first.
This ROM contains what looks like code in the first half or so. Then a
large block of FFs. And then the vectors. The very top one is 'E000'
which would point to the first byte of the ROM. Most of the others are
EExx, again in the 'code-like' part of the ROM.
I agree - this sounds like a 68xx architecture.
If you can get
the exact CPU type, I may have a disassembler that will
let you peek into the startup code a little better.
It's an HD6303X. I can look up all the letters (things like the clock
rating) if you need them, but that should be enough. In any case, writing
a disassembler is not going to take me too long if I need to do it. Fortunately I do have an EPROM emulator. This is a
good idea, well worth
trying. Next thing is to get out the datasheets and find the opcodes for
jmp and nop ;-)
Assuming it is a 6801/03 compatible CPU:
E000 7E E0 00 2 JMP *
E003 01 3 NOP
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html