8085 IO ports

Adrian Graham witchy at binarydinosaurs.co.uk
Tue Jan 17 13:56:42 CST 2017

On 17/01/2017 18:22, "allison" <ajp166 at verizon.net> wrote:

>> The transport motors move fine but the head unit itself is badly rusted
>> around the edges. I also don't know what capacitance the ex-caps are since
>> they're that badly damaged but that's info I can hopefully get from the
>> other unit since that one isn't damaged internally but is equally dead.
> The important spaces are the tape head face and the backside where the
> leads are.

As luck would have it there's one on ebay right now, but it's a bit steep at
$75 + nearly as much again in shipping. Also while it would be nice to have
a fully functioning unit at the end of this I'm not sure the cassette is
worth spending much time on apart from to replace what's obviously damaged
and at least go for something that's seen by the controller.

> THe basic main board was not that expensive ass it was mostly unpopulated...
> Adding Level A though E added stuff but their cost barely doubled it to
> maybe
> the 400$ level.  At that point its S100 bus but NO S100 boards and 4K ram
> on the main board and 8K of eprom (with M$ rom basic), the 8755 with a
> 2K monitor/debugger, and uses bit bash serial IO (very minimal hardware).

Only $400-ish? I'm surprised given the functionality it had.
> I later rewrote the monitor and pulled the MDS controller, VDM-1, and
> MITS SIO, to
> a Compupro interfacer II, so now it has an early IDE disk project for
> disk (a paltry 100mb drive).   I still have it and use it.

Heh, we all remember when 100mb was a luxury :)

> Yes, but do the pins connect to other ICs now?  I've see that stuff
> remove copper and leave pads.

Yep, I've buzzed out all the lines between ROM chips as well as the RAM
refresh, that was the second thing I did after cleaning up the battery
residue and making sure I'd not had full-on socket rot like I had in my

>> I bought a test clip so I can watch every line with a logic analyser. It's
>> proved to be a useful investment!
> I must have a dozen or more with leads.  handy for its here but not
> there... why?

Indeed. New ones are surprisingly expensive though, I paid ukp20 for a 14
pin one but it's paid for itself in not having to move 14 analyser cables
from pin to pin 16 times...

Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer

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