29 Oct
2010
29 Oct
'10
2:27 p.m.
I've got my solution, that uses at most 16-pin
packages and 6 of
them, but (a) I also need a few pullup resistors, and (b) I employ a
cheat. After making Karnaugh maps of the entire 0-F decoder and
simplifying terms, I realized that I was making the job too difficult
than the rules demanded. A common 74LS247 decoder provides the "6"
with the correct "tail"; the problem boils down to creating the
letters A-F (which, interestingly, is much less complex than making 0-
9) and wire-ANDing the outputs with that of the 247.
Not what Tony had in mind, I suspect.
I don't see why not :-). As I mentioned in my earlier reply tonight, I
wasn't sure if using the normal 7-segemtn decoder helped or not (and
whether it's better to use it for 0-7 or 0-9). Thinking about it, aren't
the 'e' and 'g' segments always on for A-F? That simplifies things...
I wonder what the smallest combinatorial implemenation is using at
most 4-input NAND and NOR gates and inverters. That's for another
time when I feel bored...
Indeed...
-tony