(Sequential Circuit Design) The state diagram and block diagram of a vending machine is shown below. The vending machine is a sequential circuit that has 3 inputs and 5 outputs. The three inputs, (N,D, and Q) denote the next coin that has been deposited. (Only one coin can be deposited at a time!) The output (DC) denotes when the candy should be dispensed. The other outputs (C5,C10,C15, and C20) denote the amount of change that is to be returned to the customer.

For the following sequence of inputs, list the states that are entered in their order and the value of each output. Assume that the machine starts in the reset state (start).

a. 4 nickels are input.

b. one dime and a quarter are entered.

c. one nickel followed by two dimes.

d. one nickel followed by one quarter.


Detailed answers to tough
homework problems