DEC bus transceivers

Toby Thain toby at
Sun Oct 23 15:57:06 CDT 2016

On 2016-10-23 2:50 PM, shadoooo wrote:
> Hello,
> 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
> circuit.
> Andrea

As an electronics noob, I'm really waiting for somebody to publish their 
findings on this, comprehensively, so I can steal their labour.

Has anyone done so? Is anyone planning to do so? I know that this topic 
flares up on the list every 6 months ago in a series of disjointed posts 
and observations. The gold is hard to find (especially for aforesaid noobs).


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