3 Apr
2005
3 Apr
'05
10:43 a.m.
Right. It's *not* the 8530 SCC chip that's faulty, but it's *not* the
data bus either - there's plenty of bus activity so bit 6 isn't
permanently jammed high.
After checking the bus, I replaced the SCC chip with a socket and tried
my spare SCC chip from home (remarkably easy job as it turned out) -
gave exactly the same results on the console.
First thought : There's some other device -- maybe soemthing like an
interrupt vector source buffer -- that's being enabled along with the
Z8530. Of course this might be inside that LSI chip you mention.
I can't do much about 1 and 2 without knowing the
pinouts of the LSI
chip or having full schematics of the board :-(
Well, there's a winter-evening project for you -- draw out the
schematics.
-tony