Is this an asynchronous down counter?

  • Thread starter stobbz
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  • #1
stobbz
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[PLAIN]http://img30.imageshack.us/img30/3306/counterty.jpg [Broken]

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

Trivial question, I know :-)
 
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Answers and Replies

  • #2
vk6kro
Science Advisor
4,081
40
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.
 

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