18 Jan
2015
18 Jan
'15
2:23 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Diane
Bruce
Sent: 18 January 2015 22:05
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: VT101 8085 CPU Fault
On Sun, Jan 18, 2015 at 09:47:35PM -0000, Robert Jarratt wrote:
...
> > you more. Nice sharp edges to signals when they shift. Times that
> > look reasonable... Steady levels, and correct levels.
> It will never be steady with a scope
because the address lines won't be
a
regular waveform. That said they looked very different
on the faulty board
to
how they looked on the good board.
A remote possibility is the boot ROM is b0rked and it's simply running
around
like a chicken without a head.
That is something a good logic analyser could tell you.
I would have thought that unlikely as I would expect to at least see some
activity on the RD and WR pins, but I don't. I mean even if the ROM is bad
it would execute *something*.
Regards
Rob