Problem set 8 for CSCI 255 -- Spring 2000

Problem 1 and only (10 points)

In the 20 March lecture, we examined the state table and flip-flop implemention for the Nabs vending machine. In this assignment, you are to modify the Nabs machine in a couple of ways. First, you are to remove the button. This will reduce the number of input symbols from four to three. Second, you are modify the state table so that the machine will now dispense candy as soon as it contains at least fifteen cents. This should reduce the number of states from four to three. You should then show how to implement this three-state machine with JK flipflops.

For this problem set you should turn in both the state table and a "truth table" implementation of the combinational circuit that generates the output and drives the JK flipflops. In Homework 4 you will implement this circuit in diglog.

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