30 Mar
2006
30 Mar
'06
10:35 a.m.
I had written....
Well, you've found _a_ problem :-)
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.
On the DL11-W I was using, the BUS LTC L signal can be seen going in pin 9
of the 7414, but it doesn't come out on pin 8. Problem identified :) I then tried two other DL11-W cards, and made sure that both
of them showed the LTC
in on 9 and out clean on 8. They do. So I ran the DL11-W diag on both these
OK, so there's probably nothing wrong with the power supply or power
harness, or backplane wiring.
The 7414 is a pretty cheap chip, and not hard to find (I think you want
to keep the same family as the original here, though -- that is don't use
a 74LS14). I would change it on the card where you know there's a problem
ansd see what happens.
other cards, and it fails for different reasons.It
prints the normal diag
startup message, followed by "01 devices under test" and the cpu halts. I
find it hard to believe both fail the same way, so I suspect something else.
Well, I've had multiple indentical devices all fail the same way, and
make me look for a fault elsewhere, where it isn;t (if you see what I
mean).
You haev too many unknowns IMHO. You don't _know_ that any of the boards
are working.
OK, is the halt a genuine one or not? In other words did it halt on a
HALT instruction, or because there's something wrong with the procesor?
It's possible there's something seriously wrong with the interrupt
arbiter logic, I think...
Per a suggestion from another listmember, I'm going to remove all the I/O
cards, put dual grants in, and ring out the 4 bus grant lines across the SPC
slots and see if there is a break somewhere.
Good idea, although why this would halt the CPU (as oposed to hanging the
bus) is another matter.
-tony