VT101 8085 CPU Fault

[Johnny Billquist]

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
>
>> -----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
>>>> =
>>>
>>
>>
>> --
>> Dentopedalogy is the science of opening your mouth and putting your foot
> in it.
>> I've been practising it for years.
>> -Prince Philip
>


-- 
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