Asynchronous down counter.

[stobbz]

Hello, this is a fairly trivial question but I can't seem to find an answer anywhere.

How is an asynchronous up counter converted to become a down counter?

Do you simply take Q' to the next flip-flop clock as opposed to Q? Like this? (Assuming JK inputs are high)

**broken link removed**

 

[MrAl]

Hello there,

How about take your outputs from the Q' outputs instead of the Q outputs ? (Q' represents the "Q not" output)
That will give you a down count with the normal connection of Q outputs to next stage CLK inputs which is the way you normally connect them for an up count. So you'd just be taking your outputs from the inverted Q outputs that's the only difference.

In fact, you can get an up count and a down count at the same time this way simply by taking the up count from the Q outputs and the down count from the Q' outputs. Note however that when the up count is at 0000 the down count is at 1111.

 

[stobbz]

That solves my problem perfectly, thanks a lot!