On 03/02/2017 16:41, "Jon Elson" <el...@pico-systems.com> wrote:
> On 02/03/2017 02:55 AM, Adrian Graham wrote: >> Ah yes, sorry, I'm aware of that. What I meant in this >> specific case is that with 4 2764s right next to each >> other with a direct signal path between adjacent address >> and data pins that has a resistance of 0.5 ohms pin to pin >> surely I should be able to put a clip on each (for >> example) A4 address line and see the same pulse at all >> four channels? > Well, if the two logic analyzers were synched together, or > you were sampling at 100 MHz or above, then yes. Neither of them can go that fast but I didn't think that was necessary since the system clock on this machine is 6MHz so sampling at 25+ should be sufficient. If I reduce the number of channels to 6 I can drive one of them at 50MHz but that didn't seem to make a difference. > totally regular square waves. If not, then the LA may not > be sampling at a regular rate, or might have gaps while > sending data to the PC. I'm just suspicious of these units, > given the results you report. So am I :) I mean, the most expensive one was ukp40 direct from China so if it's not fully accurate I can't really be surprised. I have a Zeroplus coming next week from another collector who used it on Apple][/PETs as well as car ECUs with good results. In the meanwhile the external clock signal from the 8085 on this machine is accessible in 3 locations so I'll try 3 channels and see if it's properly square. > (On my $130,000 Tektronix analyzer, I don't have to worry > about such stupid stuff, I know they got it right. I paid > less than $750 for it, it will do 100 MHz on 288 > synchronized channels, with a 128K record length. But, it > is bigger than a big kitchen microwave, and much noisier, too.) I'm looking at a lower-end HP/Agilent for around ukp200-250 which should be enough since I doubt I'll ever work on anything with a clock speed of more than 8MHz. -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?
