A parking meter accepts only quarters, which are worth one half hour each. A car may park at the meter for a maximum of 90 minutes; and the meter does not give change- quarters beyond 90 minutes are accepted, but don't increase the meter's count.
Design a FSM which controls these parking meters, using the following input and output signals:
Direction Name Description
Input q Goes high for one cycle each time the driver enters a quarter, and is low otherwise.
t Goes high for one cycle once per half hour, starting when e (expired) goes low.
Output e e (expired) is true whenever the driver has run out of time.
f6, f5, f4, f3, f2, f1, f0 A binary number indicating the amount of time left, rounded down to the next lowest half hour. As an example, if 89 minutes are left, the output on f would be 60, or 1111002.