Re: PC port question

Jamie wrote:

Michael Black wrote:

Jamie (jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx) writes:

if memory serves, -12 = low, +12 high.
and the threshold points of
+2.5 = high, -2.5 = low.
anything between that is undefined.

or has my years of work failed me?


Yes, they've failed you.

"High" and "Low" is in reference to the logic family, rather than
an absolute. so your 12V bits would never apply to the TTL family
that can never see more than 5v. (And given those voltages, it
seems more like you are thinking of RS-232 that does have something
like that.)

The logic family likewise defines the threshold point.

But, once this is all in place, the fact that there is a range of
voltages for a "high" and a "low" means that you wouldn't know
absolutely what a "high" out of a ttl gate would be. It just has
to be above the threshold, and it might vary from IC to IC (within
a certain small range) and from function to function (because the
internal circuitry varies and that affects the exact voltage when
the output is high).

Michael

if you say, so, i was talking about the RS-232 port, not the
5 Volt logic family..

have it your way, i'll stick with what i do.
thanks.


If you want to discuss serial ports then fine ! The OP was talking about
a Parallel port device !

--
Baron:
.

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