VT101 8085 CPU Fault

[Robert Jarratt]

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Diane
Bruce
> Sent: 19 January 2015 21:29
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: VT101 8085 CPU Fault
> 
> On Mon, Jan 19, 2015 at 08:48:04PM -0000, Robert Jarratt wrote:
> >
> >
> > > -----Original Message-----
> > > From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of
> > > sandy hamlet
> > > Sent: 19 January 2015 19:38
> > > To: General Discussion: On-Topic and Off-Topic Posts
> > > Subject: Re: VT101 8085 CPU Fault
> > >
> ...
> > > might have two devices trying to access the same line at the same
time.
> > > Devices on the same line may include a ram, rom, I/O ports, etc.
> > > This could cause the processor to "hang up" and act erratic.
> > > A schematic of the board would be helpfull if you have one.
> 
> Something like
> https://archive.org/details/bitsavers_decterminachematicFeb82_6949589 ?


Unfortunately not. I already have that print set, but it is for the VT100,
this is a VT101 and the terminal controller board is different. Looking more
closely at the VT100 basic video board, some of the ROM part numbers are
similar to the ROM I have, but not the same. On the VT100 they seem to be
8316s which are mask programmable. I don't know if that applies to the ones
used in the VT101. If they are mask programmed then there won't be much I
can do if the ROM is bad, unless it is possible to find pin-compatible
programmable parts and a ROM image from somewhere. 

Regards

Rob