-----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