VT101 8085 CPU Fault

Robert Jarratt robert.jarratt at ntlworld.com
Mon Jan 19 03:07:28 CST 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of tony
> Sent: 19 January 2015 08:05
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: VT101 8085 CPU Fault
> >
> > I just found something interesting, the pin activity on the address
> > lines, RD, WR, ALE etc appears normal for a bit, and only after a few
> does it all become inactive.
> >
> > Perhaps this really is an indication that the ROM is bad, if it is
> > getting into some kind of loop where it does no external activity. I
don't really
> know the 8085 to know whether that is possible.
> What if (due to ROM or RAM problems maybe) the 8085 executed a HLT
> instruction?
> -tony
> =

Good point. The S signals seem to tell you if it is halted, I will check
this evening.

I was trying to identify the chips on the board to see if I can identify the
ROMs but I can't find some of the numbers. The only socketed component is
marked CN55004N 8232 DEC TP03 23-028E4-00, could that be it? Anyone have a
datasheet for it? It would be good to try to read its contents.



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