29 Mar
2006
29 Mar
'06
5:19 p.m.
Tony wrote...
If the input signal is noisy, or something like that
you might get
spurious results.
It looked noisy to me!
What have you connected the ground lead of your
'scope probe to?
When measuring BUS LTC L at CD1, I used CC2 as my ground
reference. Just
before that I put the scope between CC2 and CA2 and got a nice non-ripply
+5v trace. I should point out that the ground clip on my probe is a bit
large for clipping to a backplane pin, so I used an alligator to microclip
extension that is about 8 inches long. Surely that wouldn't mess up the
signal that badly.
Have you tried fiddling with the trigger level (and
other trigger
controls) on the 'scope?
Yup, I'm used to doing that and generally can get
a stable trace. With this
signal, I was unable to do so.
Assuming you can read thsoe, you should see the LTC L
signal coming in on
CD1 and going into a 7414 gate. My next test would be to look at the
output of that gate with a 'scope. You should get a nice square wave at
mains frequency there.
Good idea. The 7414 is at E45, CD1 goes in pin 9 (4a) and
out pin 8 (4y).
I'll ground the scope at pin 7 and see how the signal looks. If the issue is
bit 7 in the RTC is not setting (according to the diag), and I get a good
clock out of the schmitt trigger, I assume the next thing to check is the
pin 8 output of the flipflop the trigger drives? That seems to be where bit
7 comes from.
The interurpt logic does not require LTC L to work.
Ok gotcha. I still suspect something with trap/interrupts being broke. But
more on that later :)
Thanks for the direction Tony!
Jay