TTL 101 was Re: troubleshooting help

Bob,

Although many are saying 0v and 5v, that is not "really" correct.

What TTL** WILL guarantee is that a logic "0"(Lo) will be LESS
than .8v and a logic "1"(HI) will be MORE than 2.4v

I know that Jon, Alan, and the other electronics guys know this
already. We casually speak of 0 and 5v(knowing the "truth"), but
since many on this list do NOT know already; and may be using a meter
to "check", I thought it would be worth mentioning...

Many times a "measured"(typical) HI will be about 3.3v, and a
measured Lo about .4v...

**Transistor-Transistor-Logic. The basis for the original IBM PC
parallel port circuitry. Nowadays the ports use different electronic
means to accomplish the same ends results.

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> Bob Bachman wrote:
>
> > Please explain ' inverted pins '.
> >
> > Does this mean the pins are normally at 0 volts and goes to -5
volts with
> > input?
> > Or are the pins at +5 volts normally and go to 0 volts with input?
>
> Yes, this is what he means. The program writes a '1' to that bit,
and
> the pin goes from +5 to 0.
>
> > An uninverted pin would normally be at 0 volts and go to +5 volts
with
> > input, right?
>
> Yes, a '1' to that bit sends the pin to +5 V.
>
> Jon