DEC bus transceivers
shadoooo at gmail.com
Sun Oct 23 13:50:30 CDT 2016
surely the old transceivers are the most compatible solution, however you
still need to convert the voltages back and forth...
Plus the solution is not the cheaper, and a little uncomfortable too, as
you need to find these old chips, hoping not to buy fake chinese duplicates
(it happened to me more time unfortunately).
So I was searching a solution with modern components, but not using
components too much specific and difficult to be found.
As we need 3.3v logic, but able to work in 5v bus, I'm thinking about 5v
tolerant standard logic as TI LVC or LVT.
The problem is that there aren't open drain bus transceivers, but the
problem could be solved simply using input-only and output-only components,
connecting two in parallel but opposite direction on bidirectional pins.
So identifying one or maybe two codes would be enough for all the
components needed for the board.
The idea of using bare transistors seems to me too much simple.
Not that it couldn't work, but it would be almost impossible to satisfy all
the specifications of the bus in this way... unless you use a more complex
circuit with precise current sources and resistors to grant correct voltage
biases, impedances and slew rates, which in the end is a logic integrated
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