lynchaj at yahoo.com
Sat Jan 30 21:19:25 CST 2010
It always suprised me that hre BBC micro used the 6502 rather than the
6809. By the time the Beeb was designed, Acorn had made a 6809 processor
board for their System machines, so they must have had experience with
the chip. THe Beeb is nice, but a Beeb with a 6809 processor would have
been something else :-)
Hi! When I designed the N8VEM 6809 host processor it is loosely based on an
article I read for the BBC computer called "Dragon in the tube". I am not
very familiar with the UK microcomputers but apparently 6809 "coprocessors"
were fairly common peripherals on their Z80 and 6502 designs. I used a
similar concept for the N8VEM to allow its Z80 SBC to access the 6809 as a
"host processor" peripheral on the ECB.
One of the builders was able to get CUBIX running on the N8VEM 6809 host
processor using the Z80 as its "IO processor". However, I can see how the
implementation can get confusing because it is either a Z80 based system
with a 6809 coprocessor or a 6809 based system with a Z80 IO processor. In
reality it doesn't really matter but it's a matter of perspective.
The N8VEM 6809 CUBIX implementation allows the use of ECB peripherals like
IDE, video, floppy, serial, parallel, etc but it requires the Z80 to serve
all the IO based on 6809 commands. I added the 6809 IO mezzanine board
(power, ACIA, PTM, 2 VIAs, expansion bus) to give builders the option of
using the 6809 host processor as a stand alone computer or to add separate
IO to the N8VEM system when connected to the bus. The idea being to let the
6809 host processor interact with the outside world using its own IO and
only involve the Z80 when absolutely necessary.
The hardware seems to work OK but we'll see where the software goes. I
think with CUBIX the 6809 N8VEM system becomes a lot more practical. The IO
mezzanine fits on top of the 6809 host processor. You can see some photos
here. These are out of date but give a good idea. Recently I fitted an
improved serial cable and the nylon standoff hardware. Also the PTM seems
to be working and that's good.
I have many 6809 host processor and IO mezzanine PCBs so if anyone is
interested please let me know. This would be a great opportunity for anyone
who would like to do some 6809 hardware and software hacking.
I think the N8VEM 6809 host processor is the only system I am aware of other
than Dave's homebrew that is running CUBIX. There maybe some other homebrew
systems out there too I can't find them after some searching.
Thanks and have nice day!
More information about the cctech