Man, I haven't delt with 7400's in years. Fun to be getting my hands dirty again.
BTW, if one clicks on "reply" it replies to the author, not the mailing list. A few of my mails didn't make it onto the list as a result, sorry about that whomever got them. 8) ---- Timothy Normand Miller <[EMAIL PROTECTED]> wrote: > ---------- Forwarded message ---------- > From: Jack Carroll > > > Historically, original 7400 logic could sink much more current to > ground than it could pull high, and the logic-low value was better-defined. > So if there was any risk of other signals coupling to a clock line, it made > the most sense to change state on the negative-going transition, or to > enable other devices on a logic-low. Also, if you needed to drive power > loads such as early LEDs or small relays without a buffer transistor, there > was a chance you could do it with a current-sinking output, but not a > sourcing output. Most TTL derivatives, such as LS, were like that. These > days, most late CMOS such as HC and AC is symmetrical. Be careful with HCT > or ACT, though; they have unsymmetrical input logic levels, for best noist > immunity when driven by TTL. > > > -- > Timothy Normand Miller > http://www.cse.ohio-state.edu/~millerti > Open Graphics Project > _______________________________________________ > Open-graphics mailing list > [email protected] > http://lists.duskglow.com/mailman/listinfo/open-graphics > List service provided by Duskglow Consulting, LLC (www.duskglow.com) _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
