N8VEM Disk IO peripheral

Andrew Lynch lynchaj at yahoo.com
Sat Sep 6 11:16:22 CDT 2008


A while back I mentioned the N8VEM SBC which is a new Z80 home brew project
designed in the "classic" late 1970's style.  There was some discussion
about the merits of using RAM/ROM drives versus "real" drives like IDE hard
drives and floppy disk drives.

Work continues on the N8VEM project to include supporting "real" drives.
The SBC PCB and the ECB backplane PCB are basically done and available for
builders to make their own home brew Z80 CP/M computer.  The next project is
an ECB bus monitor, which is basically done awaiting the PCB order, and the
next project is the Disk IO board.

I am currently working on the Disk IO board as my main activity.  The Disk
IO board is comprised of two parts; an IDE interface and a FDC interface.

The IDE section is basically done, works just fine, and is supported in the
CBIOS.  No doubt it could be improved with some TLC but it works well enough
for my purposes.  Like the rest of the N8VEM project, it is comprised of
"standard" commonly available DIP parts with no custom or programmable
elements except for the SBC EPROM.  

I am currently working on the FDC section and making some progress thanks to
some wise and very helpful persons (you know who you are!)  The design
exists, is based on a NEC 765 reference design at the ALPACA project, and a
working but obviously still in development prototype board is on my bench.  

As part of the development, I am writing a "disk monitor" program to
exercise the i8272 FDC chip.  Currently, I can use it to read sectors from a
320K IBM PC MS-DOS formatted 5.25" floppy disk in a Tandon TM100-2A
minifloppy drive, print status, dump sector memory, etc.

If anyone would like to join in the development of the Disk IO board, please
contact me to discuss.  I am making slow but steady progress but am sure
having another set of eyes to review and write code would help a lot.  This
would be a great way to make your own Z80 CP/M home brew computer WITH
"real" drive support.


Thanks and have a nice day!

Andrew Lynch

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