21 Jan
2017
21 Jan
'17
1:39 p.m.
On Sat, Jan 21, 2017 at 4:27 PM, Adrian Graham
<witchy at binarydinosaurs.co.uk> wrote:
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.
-tony
Back to the Executel after a few days relaxing :)
On 17/01/2017 20:59, "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).
[...]
Yep, on
the left two. I haven't dared to pull them from the board though
even though they're socketed.
Do be careful, the substrate is a brittle ceramic material... I have, a small 16 channel one that's Saleae Logic
compatible so I'm slowly
learning how to drive that too. I should be able to decode addresses and
suchlike using it shouldn't I.
Can you clock the analyser from an external input rather than sampling
every 10us or whatever? If so, clock it from the Rd/ signal and grab the
16 address lines (8 on the processor pins, 8 on an address latch, most
likely a 74LS373, which you will have to find!). Now you can see the
sequence of locations that the CPU is reading. Most (but not all) will be
instructions. Find one, compare with the listing, see if the sequence makes
sense.