>> >And thereing lies the problem. Presumably you need to program an EPROM
>> >with the firmware for this 6809. Which is somewhat hard without a
>> >programmer :-)...
>>
>> For some perhaps - at the time, myself, and almost everyone I knew worked
>> for companies with programmers, so it was not a problem. You could also get
>
>You were lucky. I was a student at the time, and in fact I built the
>program over an Easter vacation one year. I didn't have access to a
>programmer -- that's why i needed to build one.
Agreed with all your points that it may not have been possible - but I did
learn many avenues to work around such problems - when I was a student, I
"found" the only programmer in the place and got to know the guy who was in
charge of it ... :-)
My "not available" story: I was at my parents home over a long weekend when I
finally got my wirewrapped 8080 system to the point where it could use a keyboard
- as they lived in the country, there was no chance of scrounging one (I couldn't
afford to BUY anything back then), so I decided to build one...
Picture a flat piece of wood, at each key location is a metal thumbtack with a
bit of fine wire (salvaged from a transformer) attached. Two spacers at each
end allow another "board" to live about 1/4 inch above it. It had holes drilled
over every key (thumbtack), and in each hole was a nail pointing up, going
through a spring (springs came from an old contruction kit) into a hold drilled
into a short piece of dowling which was the "keytop" - another bit of fine wire
shoved into the hold beside the nail made the top contact.
The contacts from the "keys" went to a rather large and unsightly mess of diodes
(salvaged from an old Burroughs posting machine) and ultimately to a set of 8
transistors, which game 7-bit ASCII and a strobe. Took me most of the weekend to
build the thing, and it actually worked! Although it was not the most pleasant
thing to type on (rollover ... we don't need no steenking rollover :-)
One of the few things from my very early digital experiences that I really wish
I had saved...
[It was replaced within a couple of months with a real keyboard (scrounged) and
remapped to ASCII with a 1702]
>Unless your programming skills are perfect (and mine are not), this gets
>boring fast when you have to wait a few days for each update. In fact the
>time taken to erase and reporgram an EPROM yourself soon becomes painful,
>that's why I included an emulator in my programmer.
>...
>> I didn't program the actual firmware right away - I made a EPROM (at work)
>> with my 6809 monitor program in it, which allowed me to download code into
>
>Right... Again this assumes your monitor is debugged.
In this case, it was - I did a *LOT* of 6809 code in those days, both privately
and commercialy - I had my own debugger (still around essentually unchanged as
the MON09 debugger I list on my site), and I designed my EPROM programmer to
have the same serial port devices (6551), and RAM in the right place for the
monitor to run (ROM was at E000 of course - 8k at top in 6809 map).
Had I not had a debugged monitor, I would have written a very simple loader.
Just enough to get a "real" loader into the machine - unless I really cocked
it up, that would be all I needed, and I doubt I would have had to have the
ROM made more than once (did similar things on many other projects).
I selected the 6809 in the first place because I had recent experience with it
and suitable tools available...
>Incidentally, I've built a couple of instruments with microprocessors (as
>opossed to microcontrollers) controlling them (actually I normally used
>the 6809 -- nice chip), and I included commands to read/write/execute
>from any location in mmeory. Sure helped debugging !.
Yup - 6809 was an incredible chip - easy to multitask (and most people don't
know what DP is for!) - I always include low level debugging features/commands,
can be absolutely essential at times.
>> If I were doing the same project today, and had absolutely no access to any
>> means of programming the initial EPROM, I would first post in the local groups
>
>These days I'd either use a PIC as the controller processor (trivial to
>make a programmer for, and the programming algorithms are documented), or
>if I was using some deviec with external program memory, I'd start off
>using E2PROM or something, again easy to make a programmer for. I now
>have access to rather more computers, with rather more user I/O lines...
Yeah, OK - I would use some little flash device too - I was speaking in terms
of if I were faced with the same problem to build exactly the same type of
device with similar parts ...
>This was long before the days of the Internet in the UK. It wasn't easy to
>find places to ask about borrowing a programmer.
Not familier with UK companies etc. - this would have been somewhere in the
mid 80's, and I was reasonably well past being a student ... but these are
the kinds of things I would have tried had I still been in school:
- Local companies that were "friendly" ... might involve having a friend
who's dad worked there.
- Local shops, schools etc.
- BBS systems - lots of other "geeks" hung out there, many with good
connections... fidonet was king before the internet.
>> I guess what I am saying, is that if you are not prepared to be a little
>> creative, you are probably not well suited to designing/building your own
>> test equipment.
>
>Are you saying I'm not creative?
NO! that was a general comment, and NOT directed to you specifically.
- I know you are creative (from your postings), and you did solve the problem
- no need to defend your honor any further.
but.. especially in todays world (as you point out), having to get the "first"
ROM programmed should not be a show stopper. Even that is only an issue if the
OP decided to build my design "as is" - as discussed earlier in this message,
a little flash device could be used and then all you need is a serial or parallel
port to program it (depending on the requirements of the device). To me (primarily
a software guy), using a little controller with lots of I/O and ability to time
pulses far more accurately than winblows, it still makes sense to design a micro
based device.
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Vintage computing equipment collector.
http://www.parse.com/~ddunfield/museum/index.html
Received on Thu Jul 29 2004 - 20:32:25 BST