1. ECE 3130 – Digital Electronics and Design Lab 6 State Machines Fall 2012 Allan Guan

2. What is a State Machine? A model of a machine that can be in one of several states (e.g. traffic lights) Different representations: – State tables – State diagrams – State equations Allan Guan

3. Mealy and Moore State Machines Mealy machine – Output values are determined by both the current state and the current inputs Moore machine – Output values are determined solely by the current state Allan Guan

4. Objectives Design both a Mealy and Moore machine to detect the sequence, 1010, in a bit pattern Draw a state table Implement a Mealy machine using D flip-flops Allan Guan

5. Moore Machine Present State Next StateOutput Input=0Input=1 S 1 (000) S 2 (001)0 S 3 (010)S 2 (001)0 S 3 (010)S 1 (000)S 4 (011)0 S 3 (010)S 2 (001)0 S 5 (100)S 1 (000)S 4 (011)1 Allan Guan

6. Mealy Machine Current State Next StateOutput Input=0Input=1Input=0Input=1 S 1 (00) S 2 (01)00 S 3 (10)S 2 (01)00 S 3 (10)S 1 (00)S 4 (11)00 S 3 (10)S 2 (01)10 Allan Guan

7. Mealy Implementation using DFF Inputs of combinational circuit Output of combinational circuit Present stateInputNext stateFlip flop inputs output ABxABDADBy 00000000 00101010 01010100 01101010 10000000 10111110 11010101 11101010 Allan Guan

8. Circuit Implementation Allan Guan

9. Output Allan Guan