Question

The California student chapter is co-sponsoring a tea vending machine with a heavily subsidized price of 15 cents a cup. Design a Mealy FSM for the vending machine assuming the students can load nickels (input N) and dimes (input D), only one coin at a time. If the user tries to enter two coins at the same time, the vending machine would not allow it, i.e. it will stay in the same state. If the user pays more than 15 cents, no change is dispensed (i.e. if the user enters a D when the running sum is 10 cents, the FSM will count the total as 15 cents and dispense no change). The vending machine will dispense the product (output P will be pulled High) as soon as there is enough money entered and then reset unconditionally. Use the following format for the inputs: ND. Use active-high logic to indicate an input or output is active. Show the state transition diagram, state assignment table, state transition table, next-state equations, and output equations. Use K-maps to extract the most simplified equations.

Answer 1

The following is the mealey machine of the given vending machine:

N denotes nickel and D denotes dime.

The starting state is q0. The accepting state is q15.

This is a mealey machine so the outputs are shown for each possible input symbol from each state.