Skipping "zero" with a counter?

[eromlignod]

Hi guys:

I'm working on an application where I'd like to have a two-bit counter
that needs to continuously count 1, 2, 3, 1, 2, 3, 1, 2, 3... in a
loop. I don't want zero. It is controlling three of the four
channels of a mux and the zero channel is "off" (no signal), so I want
to skip it.

Is there an easy way to do this, or do I need to build my own counter
with logic?

Don

 

[Mike Silva]

If you need a 2-bit binary counter, you can do this with a pair of J-K
flip flops and some wires.  I don't know for sure, but I think you can
get just about _any_ 2-bit sequence you want from a J-K flip-flop pair
without additional logic.

(It would be interesting to know just how far this extends -- can you do
this with any three-bit sequence and three J-Ks?  Four? Five?)

J-K flip-flops, what a blast from the past. Can't remember the last
time I needed them. But you're right, that's a very clean solution, a
single dual-FF package. I warmed up the long-forgotten neurons and
came up with this solution

Ja = B, Ka = B
Jb = 1, Kb = !A

I used to love solving those problems.