[time-nuts] RS 232
Chuck Harris
cfharris at erols.com
Fri Jul 26 17:11:47 UTC 2013
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
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