RS-232 Tx / Rx monitoring LEDs?

[Paul Koning]

> On Aug 20, 2015, at 3:40 PM, Eric Smith <spacewar at gmail.com> wrote:
> 
> On Thu, Aug 20, 2015 at 10:54 AM, Paul Koning <paulkoning at comcast.net> wrote:
>> Ok, but when you refer to "drive strength" I assumed you were talking about current, not voltage.  By that measure totem pole outputs are pretty much symmetrical.
> 
> Not for true (bipolar) TTL.  See the specs for the 7400, 74LS00, 74S00:
>    http://www.ti.com/lit/ds/symlink/sn74ls00.pdf
> 
>          Ioh(max)  Iol(max)
> 7400      -0.4      16
> 74LS00    -0.4      8
> 74S00     -1        20
> 
> CMOS for comparison:
>    http://www.ti.com/lit/ds/symlink/sn74hct00.pdf
>    http://www.ti.com/lit/ds/symlink/sn74act00.pdf
> 
>          Ioh(max)  Iol(max)
> 74HCT00   -4        4
> 74ACT00   -24       24

Ok, clearly my memory was faulty.  Thanks for the corrections.

	paul