18 Jan
2015
18 Jan
'15
12:48 p.m.
On 2015-01-18 21:37, Robert Jarratt wrote:
No stuck, high.
Is there any activity on any of the address pins? If those also are
dead, either the whole CPU is dead, or else it is disabled by something.
If those are showing activity then the RD pin is either dead, or shorted
somewhere, I'd guess.
I hope you are checking the right pins... :-)
Johnny
Regards
Rob
--
Dentopedalogy is the science of opening your mouth and putting your foot in it.
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Bob
Rosenbloom
Sent: 18 January 2015 20:11
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: VT101 8085 CPU Fault
On 1/18/2015 12:07 PM, Robert Jarratt wrote:
> No, I checked that and it isn't. It is an active low signal and it is
high.
Regards
Rob
What about the READY pin? Stuck low?
Bob
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of tony
duell
Sent: 18 January 2015 19:16
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: VT101 8085 CPU Fault
> The terminal controller board on my VT101 is not working, if it
> displays anything it is random characters. I have used my scope to
> check the 8085 CPU. It has power, it is outputting a valid clock,
> but there is no activity on the RD,WR and ALE pins. I am guessing
> the 8085 is bad, but before I go replacing it I wanted to check if
> anyone knew of anything else that might cause the 8085 to misbehave
> (ie am I seeing
symptoms or a cause?).
What is the state of the reset input to the 8085? In other words, is
the
CPU
being held reset all the time?
-tony
=
I've been practising it for years.
-Prince Philip