3 Jun
2006
3 Jun
'06
3:35 p.m.
I've been wondering for a while now what the major
use was of those
"AND-OR-Invert" gates, since the early TTL stuff I became familiar with
first had a bunch of them in the databook...
Anybody know?
A couple of thoughts
1) It's fundamentally a sum-of-products circuit (OR of ANDs). This is one
standard way to genrate an arbitrary logic function
2) It's also the basic circuit of a multiplexer. If you want a mux where
you can enable several inputs simulaneously, or where the select lines
can't easily be turned into n binary-encoded lines, then an
And-OR-(invert) gate is esseintally what you're going to use.
3) Rememebr a PAL is fundamentally a set of AND-OR-(invert) gates with
programmable input wiring. Before there were PALs you got to use the AOIs
and wire the inputs by hand :-)
-tony