(a) Add a count-down timer mode to the wristwatch module of Figures 11-2 and 11-3. The timer should count seconds, minutes, and hours. When in the timer state, B2 should change states to allow setting the hours, minutes, and seconds with B3. When setting is complete and the wristwatch is back in the main timer state, B3 should start the count-down. If B3 is pressed again, it should stop the count-down; otherwise, the count-down stops when it reaches 00:00:00, in which case the timer beeps for one second.
(b) Modify the test bench and test your timer.
