8085 IO ports

[Adrian Graham]

On 21/01/2017 21:39, "Tony Duell" <ard.p850ug1 at gmail.com> wrote:

>> I don't think I'll touch them, they're obviously part of the phone subsystem
>> and I doubt I'll ever plug it into a phone line - I have several One Per
>> Desks for that sort of thing if needs be.
> 
> A telephone line similator is a useful toy to have for something like
> this. I have
> an old but good one (it use a TMS320 series DSP for signal degredation) that
> I bought non working on Ebay. Reseating the socketed chips helped, replacing
> a couple of comparators and a voltage regulator fixed it -- the
> problem of course
> being to find the faulty parts (there are well over 300 ICs in the unit).

Eep, slightly more involved than my little effort then :) There's maybe 70
in this one including the 16 RAM chips and maybe 7 opamps.

>> I can trigger it on the RD signal yes. There's 2 LS373s which both had dead
> 
> Not trigger, but clock. In other words to take a sample on every Rd pulse.

This is interesting if the data is to be believed. The Saleae Logic software
contains several decoders like SPI, I2C, Analog Serial and 'simple
parallel'. The official docs say external clocking isn't supported but the
'simple parallel' decoder can work in a similar way if you nominate one of
the 16 available channels as a clock channel. It's supposed to cover a 16
bit data bus but if I take a 10 second sample of A0-A14 and RD then map
those address channels to the analyser's data channels and tell it to clock
using RD I see a definite repetitive pattern. More reading of that tomorrow
since I've just noticed what time it is!

Cheers,

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