Fall 2014 CSCI 255 Homework 5

This assignment is should be uploaded to Homework 5 on moodle by 5:00 PM on Friday 26 September.

There are two parts for this problem.

Implementation of Finite State Machines

Problem 4 of Homework 4 asked you to draw a diagram or create a table to represent the finite state machine representated by the following Java methods.

    enum State { S0, S1, S2 } ;
    
    private static char output(State presState) {
        return presState == State.S0 ? '1' : '0' ;
    }

    private static State nextState(State presState, char inChar) {
        State nxtState ; 
        if (inChar == '0') {
            if (presState == State.S0) {
                nxtState = State.S0 ;
            } else if (presState == State.S1) {
                nxtState = State.S2 ;
            } else /* presState == State.S2*/ {
                nxtState = State.S1 ;
            }
        } else /* inChar == '1' */ {
            if (presState == State.S0) {
                nxtState = State.S1 ;
            } else if (presState == State.S1) {
                nxtState = State.S0 ;
            } else /* presState == State.S2*/ {
                nxtState = State.S2 ;
            }
        }
        return nxtState ;
    }

Or you can use this tabular representation of the next state function.

Or of the output function.

For this homework, you are to implement this finite state machine in Logisim. Try to keep it simple. You can use AND-gates and flip-flops or you can use a ROM and register.

Be sure to include a reset line for starting your circuit in the right state.

Testing of the Finite State Machines

Describe your plan for testing your finite state machine. This should be a couple of paragraphs long.

What to turn in

Turn in the Logisim .circ file for your implementation and and either a text or PDF file describing your testing strategy.