> Basically, Olin is suggesting that you take two Schottky diodes (D1 and
> D2),
> and:
>
>    - Connect anode of D1 to the signal line, and cathode to Vcc
>    - Connect cathode of D2 to the signal line, and anode to Gnd
>
> What this will do, is protect the Rx input by keeping the voltage on the
> signal line from going above Vcc, and below Gnd.

... by more than a Schottky diode drop in each case.

In practice this violates the spec sheet requirements in SOME cases and not
others BUT works OK in *almost* every case.
YMMV but usually won't.

Note that the current able to flow through the series resistor must be less
that the supply current if the supply rail is not to be "pumped up" by ths
system. This is almost never a problem, but has causght some people out in
special situations.



                  Russell



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