RTL Logic

From: Steve Thatcher <melamy_at_earthlink.net>
Date: Sun Jan 9 08:37:09 2005

well, I design by specifications. The TI specs say that the short circuit current for 74xx series is 18ma which is also not within specs for the general output current capability of 16 ma. Transient shorts like this are a great way to generate power supply noise. I guess I never applied any type of "preliminary hackery" to systems I have developed.

-----Original Message-----
From: der Mouse <mouse_at_rodents.montreal.qc.ca>
Sent: Jan 9, 2005 5:15 AM
To: cctalk_at_classiccmp.org
Subject: Re: RTL Logic

Except that totem-pole outputs usually have just a transistor to
ground, but a transistor and resistor to Vcc. This means that the one
driving the signal low will win, and, provided not too many outputs are
wired together, it will sink the current without damage. (I've
actually built circuits that depended on this, though I've never liked
it and never considered it suitable for more than preliminary hackery.
I've also always never done it for anything where the conflict will
last more than nanoseconds, as when building an ~R/~S flip-flop out of
two cross-coupled inverters rather than the more usual NANDs or NORs.)
Received on Sun Jan 09 2005 - 08:37:09 GMT