[sdiy] Update ... and a warning

[Ingo Debus]

Tim Ressel wrote:
> I just built a dual UART board for my nifty new
> development system. I wanted to verify the address
> decoding was working right, so I got out my borrowed
> 60MHz scope and checked the chip select line that
> comes out of the processor.
> 
> No pulses.
> 
> Then I did a sanity check and looked at the select
> line for the RAM chip on the dev board.
> 
> No pulses.
> 
> I haden't checked the RAM to see if it actually
> worked, so I did a memory check. It worked. Ahhh....
> I got out my el cheapo Radio Shack logic probe and lo!
> there were all the missing pulses.
> 
> The moral of this story is: test equipment can lie,
> decieve, mislead, and in general be a pain. So always
> double check your measurements and make sure your
> scope ain't hiding your pulses!

Now I'm really curious why your scope didn't catch the pulses. How 
long are the pulses supposed to be? What kind of probe did you use? Is 
it an analog scope?

Ingo