Is this an asynchronous down counter?

[stobbz]

[PLAIN]http://img30.imageshack.us/img30/3306/counterty.jpg

Is this an asynchronous down counter, or is it nonsense? (Assuming all J and K inputs are connected high)

Trivial question, I know :-)

 

[vk6kro]

Yes, it is an asynchronous binary counter that counts downwards.

However, it would have problems with propagation delays and these would cause the outputs to be wrong for a short period after some of the clock pulses.

I put the circuit into a simulator that includes propagation delays and it showed up a large number of glitches in the output.

So, you get the following (with glitch outputs shown in brackets):

0
(1)
(3)
(7)
F
E
(F)
D
C
(D)
(F)
B
A
(B)
9
8
(9)
(B)
(F)
7
6
(7)
5
4
(5)
(7)
3
2
(3)
1
0

So, it would be OK just as a divider but not for any serious counter application.