8085 IO ports

Adrian Graham binarydinosaurs at gmail.com
Tue Jan 17 10:38:02 CST 2017

On 17 January 2017 at 02:14, allison <ajp166 at verizon.net> wrote:

> <http://bitsavers.informatik.uni-stuttgart.de/pdf/intel/MCS80/MCS80_85_Users_Manual_Jan83.pdf>
> That's the later 1983 version but its the book you want.

Thanks, that was some light reading over lunchtime. The descriptions of the
interfacing helped a lot so tonight I need to finish tracing out the
SAA5070 LUCY circuit and the non data bus lines going to the keyboard
because I've not found anything that (I'm guessing) should interrupt the
CPU to say there's been keyboard activity.

> On the tape drive controller board are a pair of very messy 25V caps that

> > thought had rotted because of damp - the tape transport itself is
> probably
> > beyond saving through rust - but could they have exploded I wonder.
> >
> Likely history but if the parts move and the head is ok then clean it
> really well replace the caps and try.

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.

> >> in that system working to this day (along with a 8085A subprocessor).
> > Strewth, that's some troubleshooting effort!
> I had bought the Netronics explorer 8085 just before that bolt.  That
> gave me
> a S100 chassis that would run even bad cards (think SDK85 with S100 bus
> interface).

Just googled it, that must've been expnsive when it was new!

> The turned pin are heavy and will stand that.... the copper under them
> or leading to them may be gone

I tested the sockets by resting the board on a sponge wrapped in tin foil
connected to one lead of my DMM.

> FYI vinegar or lemon juice will neutralize it, the battery (likely nicd)
> is alkaline.
> Rinse with water and dry.

Oh yes, that was the first thing I did when I removed the battery :)

> You can always inject a really slow processor clock, isn't rated for it
> but it does
> run down to less than 1khz. You can then watch signal with a bunch of leds.

I bought a test clip so I can watch every line with a logic analyser. It's
proved to be a useful investment!

Owner of Binary Dinosaurs, the UK's biggest home computer collection?

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