8085 IO ports

[allison]

On 1/17/17 11:38 AM, Adrian Graham wrote:
> On 17 January 2017 at 02:14, allison <ajp166 at verizon.net> wrote:
>

snippage>>>>>
>> <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.

Figured that may help.
>> On the tape drive controller board are a pair of very messy 25V caps that
> I
>
>>> 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.

The important spaces are the tape head face and the backside where the 
leads are.
>
>>>> 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!
As systems of the day went it was cheap as the base unit plus the upgrades
like the s100 frame, backplane and all were fairly inexpensive.  I had 
power
supply, memory and many of the parts to populate it.

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).

I caught a break as around theyn I was testing JAWS 64K S100 dram board
for Netronics in as many s100 crates as I had access to in 1978-79 
(quite a few)
so I worked a deal.  Paid less as I could get the boards and mechanical 
bits and populate
from my stocks.  The Jaws memory was the best Dram design for S100 of 
the day
as it worked in everything I'd tried 8080/8085 or z80 plus one 1802!

For the longest time the config was 64kdram board (Jaws), VDM-1, MITS SIOB,
and NS* MDS floppy controller and it ran NS*dos or CP/M as needed. 
Without S100
boards in it it had monitor and 4K ram plus basic so that was enough to 
exercise ram
cards, Io boards and the MDS controller.

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.

That's the rest of the story.
>
>> 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.

Yes, but do the pins connect to other ICs now?  I've see that stuff 
remove copper and leave pads.
>
>> 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!
I must have a dozen or more with leads.  handy for its here but not 
there... why?

Allison


> Cheers,