[time-nuts] RS 232

[Chuck Harris]

The diode would be a good idea... I forgot about that.

57.6K would probably work with the proper selection of resistors,
but you could totem pole the opto's to make them pull up and
down.

-Chuck Harris


Bob Camp wrote:
> Hi
>
> The only other thing I have seen done on opto isolated RS-232 is to add a
> protection diode on the "transmit" opto output transistor. There's a spec that
> says you have to be able to apply +/- 25 volts to any pin weather the device is
> powered up or not. If you want high(er) speed you can put a pair of transistors on
> the output of the opto to boost the drive current. Not needed at 9600 baud,
> probably useful  if you are trying to go > 100K baud.
>
> Bob