3 Feb
2017
3 Feb
'17
10:47 a.m.
On 03/02/2017 16:41, "Jon Elson" <elson at pico-systems.com> wrote:
On 02/03/2017 02:55 AM, Adrian Graham wrote:
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.
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. 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?