Design a ?disk spinning? animation circuit for a CD player. The input to the circuit will be a 3-bit binary number A ₁ A ₂ A ₃ provided by another circuit. It will count from 0 to 7 in binary, and then it will repeat. (You will learn to design such counters in Unit 12.) The animation will appear on the top four lights of the LED display of Figure 8-15, i.e., on X ₁ , X ₂ , X ₇ , and X ₆ , going clockwise. The animation should consist of a blank spot on a disk spinning around once, beginning with X ₁ . Then, the entire disk should blink on and off twice. The pattern is shown.

Design your circuit using only two-, three-, and four-input NOR gates and inverters. Try to minimize the number of gates required. Any solution which uses 11 or fewer gates (not counting the four inverters for the inputs) is acceptable.

A A A3 000 001 010 011 100 101 110