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Old 13th Jul 2019, 8:45 am   #161
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: Gemini 80-Bus System

Normally when two adjacent data lines look identical with frequent half-logic levels as they do on the uppermost two images on that page, it suggests that the two lines are shorted together either physically (track short/solder splash) or by a fault in one of the devices on the bus.

The half-levels are caused by one line (say D0) trying to go high at the same time as the other (say D1) goes low. You get a high on both lines when both lines are trying to be high, a low on both lines when both are trying to be low, and a half-level when they are trying to be in opposite states.
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