Answer the following Question :
Please design a 3-bits asynchronous counter that have both "count up" and "count down" ability. You should use 2-1 multiplexer to resolve the problem, so that you can switch between "up" and "down" with one switch.
(hint: "count up" and "count down" use different clock, which are inverse to each other. So, switching between up and down is actually changing the clock)