B
bluemoon123
- Jan 1, 1970
- 0
Hi,
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
Thanks.
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
Thanks.
Perhaps the OP meant just using gates....Tim Williams said:Gosh, it's so easy I feel dirty even mentioning type D flip-flops.
Getting a regular, specified duty cycle (such as 50%) for odd N is up to
you, though.
Tim
Yes I meant using purely logic gates, without flip-flops.
bluemoon123 said:Hi,
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
Thanks.
Yes.
John Larkin said:Yup, I think so, just nand gates or something. But it will have to
have internal states, so some people might shout "flipflop!"
John
Another solution -- without flip flops this time !!
Clocked RS latches modified for edge triggering on the clock can be
cascaded -- would take N latches and you can pick off your output anyplace
along the chain to get any desired duty cycle. A clocked RS latch expands to
5 gates, and you'll probably need 2 or 3 more to make it edge triggered,
which gets you riight up there with the flip flop for gate count per stage,
but with the disadvantage of not using a counter approach which means many
more stages for larger N.
The question then becomes "just exactly HOW PURE" must the combinatorial
logic be. If you cant build latches or flipflops from gates, I dont think
its possible.
Just for grins -- here is a weird way to do it that just uses low level
gates + some analog components
http://www.wenzel.com/pdffiles/dividers.pdf
Another solution -- without flip flops this time !!
Clocked RS latches modified for edge triggering on the clock can be
cascaded -- would take N latches and you can pick off your output anyplace
along the chain to get any desired duty cycle. A clocked RS latch expands to
5 gates, and you'll probably need 2 or 3 more to make it edge triggered,
which gets you riight up there with the flip flop for gate count per stage,
but with the disadvantage of not using a counter approach which means many
more stages for larger N.
The question then becomes "just exactly HOW PURE" must the combinatorial
logic be. If you cant build latches or flipflops from gates, I dont think
its possible.
Just for grins -- here is a weird way to do it that just uses low level
gates + some analog components
http://www.wenzel.com/pdffiles/dividers.pdf
Yes I meant using purely logic gates, without flip-flops.
Hi,
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
build an N-counter in logic.
Where are you studying?
I agree--turning delay from a bug to a feature.John said:I think you can also just "walk" states through rs flops (or
equivalent feedback gadgets) on clock high and low levels, which is
not exactly edge triggering
The LC on the dflop thing is cute!
John
There is a simple way to build reliable flip flops from gates. You useRich said:Sure, it can be done. Just don't call your cross-coupled gates "flipflops"
- the professor will probably never know the difference. ;-)
(or you might lose points for coming up with a workable answer to what's
otherwise an impossible task, in which case "it's impossible" might be the
intended answer. ;-) )
Good Luck!
Rich
Hi,
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
Thanks.
Hi,
Does anyone know how a clock can be divided by N, using purely
combinatorial logic?
Thanks.