VT101 8085 CPU Fault
robert.jarratt at ntlworld.com
Sun Jan 18 16:23:01 CST 2015
> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Diane
> 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
> regular waveform. That said they looked very different on the faulty board
> how they looked on the good board.
> A remote possibility is the boot ROM is b0rked and it's simply running
> 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*.
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