On Friday 26 Sep 2003 12:08 pm, you wrote:
> I once wrote:
> >> Most RS232 receiver buffers in a pc will accept 3.0V and above as mark
> >> and anything below that as space
> >
> > I sincerely hope that this is not true because it means the receiver has
> > zero hysteresis and zero noise margin.
>
> It is true because the receiver chips are made that way. I do not make
> receiver chips, only use them. You will see in the spec sheets that the
> hysteresis can be (and is) deleted or reduced. I think that they do this
> to prevent edge ringing and cross-coupling from unmatched cheap serial
> lines at high speed to cause glitches.

Can you give me an example of such a device?

>
> >> (rs232 spec says -3.0V and below). So sending 0/5V is barely ok.
> >
> > So sending 0/5V is out of spec.
>
> Sending 0/5V is out of RS232 spec and within normally used RS232 receiver
> chip specs, as used in a PC near you. Ok ?

OK.

Ian

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