Re: RS-232 levels to computer


<pdrunen@xxxxxxx> wrote in message
news:1142015379.013518.240620@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi All,

I understand that standard RS-232 levels must be bipolar with at least
a -3V for a logic "1" and +3 volts for logic "0".

The micocontroller 232 level is TTL level, I use this signal to drive a
NPN so the the signal is inverted and use +12 on the collector to get
the level. The lowest voltage out of the NPN will be near zero. I am
using this for just collecting some data sent over a small cable lengh
and I don't plan on this being part of a design.

The question is in regards to the computer RS-232 input, would the near
zero voltage be taken as by the com port as the correct level?

Don't count on it. However, many poorly-designed, non-spec-compliant
interfaces will work with those voltages.

Sometimes.

Intermittently.



.

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