On 03/02/2017 23:29, "dwight" <dkel...@hotmail.com> wrote: > Adrian > > What you see on the other select line is what is called a glitch. > > These are not that uncommon during the early part of the address. > > What is important is that there are no glitchs when ALE transitions.
Ah, ok, there's a glitch filter that I can apply to each channel, I'll explore that. Cheers! > ________________________________ > From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Adrian Graham > <wit...@binarydinosaurs.co.uk> > Sent: Friday, February 3, 2017 2:34:18 PM > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Logic Analysers > > On 03/02/2017 19:43, "Tony Duell" <ard.p850...@gmail.com> wrote: > >> But that's why I said 'about'. I am doing order-of-magnitude calculations, >> not trying to design a delay line. I would estimate that between adjacent >> ICs on the same board you'd get a delay measured in 10's or 100's of >> picoseconds. That sort of order. So a 25MHz logic analyser, with an >> effective time resolution of 40ns (if that) is not going to show it. >> >> There is no way you're going to get delays of 40ns between adjacent >> ICs on any reasonable PCB. > > This is the sort of thing I mean: > > http://www.binarydinosaurs.co.uk/STCExecutelA1checking.jpg > > Watching the A1 address line (no triggers just sampling 6 points) and a > pulse appears at ROM4 on the falling edge of the ALE signal but not the > other 3 ROMs or the LS373 flip-flop that's demultiplexing the AD1 pin of the > 8085. While I was thinking about the possibility of propagation delay I > noticed this one: > > http://www.binarydinosaurs.co.uk/STCExecutelA1checking2.jpg > > Pulse missing from ROM3. > > Given the paths on this board aren't massive and resistance is equal between > all points when measured with a DMM (and all sockets have been replaced, > traces checked etc) what else could I be looking at? > > -- > Adrian/Witchy > Binary Dinosaurs creator/curator > Www.binarydinosaurs.co.uk - the UK's biggest private home computer > collection? > > -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?
