Merging Data

ian field

Joined Oct 27, 2012
6,536
Yes, XOR gates are definitely more fun -- in so many ways. I don't know that I would say it is merging two data streams, even though, technically, that is exactly what it is doing. I think in terms of being able to separate the data streams at the other end. But when I think about it, the same type of protocol that you would need to use and OR or AND gate to achieve transmission would work for an XOR gate, too. So I'm game.
The XOR circuit I liked was in the early multisync VGA monitors.

Both horizontal and vertical sync trains could be inverted as a means of signalling to the monitor which pre-set settings to use for the currently active mode.

Each XOR gate had a basic C/R integrator feeding one input and the sync train to the other, if the train was inverted (mostly at 5V with narrow negative pulses) the gate would invert that to a GND floor with narrow positive pulses. The integrator level was also buffered by one of the left over XOR gates and sensed by a custom IC that recalled the pre-set values from the front panel micro.

As the assortment of modes continued to grow, they also added frequency discriminators to let the micro know whar was going on.
 
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