[Techtoolslist] Fluke 9010 bus test address tied message confusion

[John Robertson]

On 2019/07/10 12:10 a.m., David Shoemaker wrote:
> Working on a space invaders board.
>
> 8080 pod, passes self-test.
>
> Put it onto UUT and hit auto.  Getting an error that does make sense.
>
> ADDR bits 13 tied-Loop?
>
> Thought at first that was bits 1 & 3 tied.  But probing around didn't find
> anything.  So I tried tying them together myself to see what happens.
>
> ADDR Bits 1 and 3 tied - loop?
>
> Uh, ok so they are explicit on the two bits tied.  That's good to know.  But
> why is it only telling me one bit?
>
> So I pulled out the manual and from the bus test error messages table there
> should never be a "bits" message without two bits.  But I am only getting
> one (and no MORE led, and more button does nothing).
>
> The only single bit error should be if bit tied low or high. But that is not
> the message (and it says "bit" not "bits").
>
> I tried exercising bit 13, did a write @ 2000 = 0, probe set on address and
> can see the line being driven high.  And no other bits are being driven when
> I check.
>
> Thoughts?
>
>   
>
> Thanks,
>
> David
>
>
When I get these errors (not specific about what it is tied too) I 
search the entire line and usually find it is shorted to something the 
CPU has no connection to. For example on the SI board - do you have the 
sub-board unplugged? Take a look in the socket for junk/bent pin 
shorting A13 to some other line (if A13 goes to that socket). This error 
simply means that the Fluke can't exercise A13 easily and it assumes it 
is stuck to some other line that the pod can't 'see'.

Have you done a Diode Test to compare A13/Vcc/GND results with A12 or 
A14? They should be the same with the Fluke pod disconnected.

John :-#)#

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