30 Dec
2005
30 Dec
'05
2 a.m.
I have an
8086/8088 monitor, which provides edit/dump memory/registers,
serial download, breakpoints, single-step, disassembly and lots of other
goodies in just over 4K of code space - completely independant of hardware
(ie: No DOS/BIOS requirements).
That's exactly the kind of firmware I want for the 8088 SBC
project, at least to start. Does your monitor use a serial
console? I need to add a serial port to the design. Possibly
using the 6402 UART. Really, though, one of the 'design
principles' of the projet is to re-use, so maybe a part from the
8250 family (which can be found on any old PC-clone serial card)
would be easier for someone replicating the design to come up
with. Awhile back I 'won' a whole tube of 85C30 parts from
someone selling them on eBay, but they never showed up. And I am
trying to stick to DIP packages to keep it easy to build with OTS
parts. Or I could stick a primative ISA slot on it and plug in
one of my spare IBM Serial Adapters and use the current loop
interface. (naw... heh.) I have fond memories of monitor-based systems from the
past. I
have a first generation BigBoard in mothballs, for one example.
It used to boot CP/M from the monitor prompt.
First thing I write when going to a new CPU is a monitor - I also have
monitors to stuff into a lot of vintage gear so that I can poke around,
very handy. If it is of use to you on the 8088 project, I also have HDM86,
one of my "Hardware Debug Monitors" - it's much simpler, but uses NO
RAM - handy for getting boards up and running.
I also have a
PC based 8086/808 cross assembler intended for the "bare
metal" which produces downloadable code.
I've noticed the full line of cross-assemblers for all sorts of
processors on the website linked at the bottom of your messages
(and I think I remember, going way back, your ad in magazines
like Circuit Cellar.) Really what has been the 'missing link' in
the 8088 sbc project has been an assembler designed like yours.
There are many MANY tools available and many websites dedicated
to x86 assembly programming, but it's almost all oriented toward
a BIOS-based PC system. I come from a 'bare metal' and prefer
starting right at the bottom from a reset vector. At one point I had the 'dream' of a monitor
rom to drop in place
on PC-XT motherboards to turn them into Single Board Computers.
But these days an Xt motherboard is a scarce commodity, while
there are still plenty of 8088 processors available. (And
keeping the design 'generic' the next generation can be an 8086
based system, with 16 bit data path.)
Thats should be relatively easy to do, especially if you stick to a
serial console, or a single video card type (MDA for example) to
support.
--
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