Dwight K. Elvey
dwight.elvey at amd.com
Fri Apr 8 15:55:42 CDT 2005
>From: "Eric Smith" <eric at brouhaha.com>
>> What kind of scope would I need and how much does one cost?
>Assuming that you want something good but cheap, your best bet is
>probably to try to find an old Tek 465. It's a good, solid two-channel
>100 MHz scope. ISTR that they show up on eBay frequently, but as
>with anything on eBay, there's no telling what condition it would
>really be in.
The only issue I've seen with the 465's is that if the
sweep frequency switch is broken ( a common failure on these ),
this switch is unobtainium.
It is good to have more than two chanels of input. It is
also useful to have the delayed sweep. Other than that,
I like others would recommend a 100MHz as a minimum. Stay
away from the 20-30 MHz scopes that are often used for TV
You need to get scope probes. These should be 10X probes
for doing digital work.
Even though Leader doesn't have a good reputation, I've
been using one of their high end scopes that has 4 channels,
150 MHz bandwidth and A/B delayed sweep. It has been a good
I still like the Tectronix better but when I bought mine
( for $75 ) the Tec's were out of my price range.
One thing that I've always wanted to build but have just
never had the time is a trigger qualifier. What this is
is a large input and gate. It might also have some sequencing
as well. Now days, this could be done with some of the
FPGA that you reload on each powerup. The idea is that many
things that you want to see in a computer need to be qualified
by a number of signal and may even require some sequencing
to make sure your looking at the right thing. Most logic
analysers do this but they rarely have good sequencing
control. This is their main weakness.
With a reprogrammable FPGA, one can write the formulas
and the state sequencing to most any level of complexity.
Of course, one can actually buy a logic analyser but
like I said, they usually have poor sequencial controls
and the display is a little too far removed from the
real signals for me. I like to see the real levels that
only a scope can provide.
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