VT101 8085 CPU Fault

Robert Jarratt robert.jarratt at ntlworld.com
Mon Jan 19 14:48:04 CST 2015

> -----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
> Using a scope, look at the address lines and/or data lines at power up, just after
> system reset.
> The pulses will probably vary in width but should all be the same amplitude.
> If you see something like stair stepping: where a pulse starts out at
> 5 volts and drops, for example to 3 volts and then drops to 0 volts, then you
> 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.

Sadly, that is the one thing that does not seem to be available. If anyone does know of a print set for the VT101 please let me know.



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