Overview

One of the most common forms of synchronous sequential circuits.

• Moore FSM
  • Outputs depend on current state only
• Mealy FSM
  • Outputs depend on current state & inputs

• State register
  • Stores current state
  • Loads next state at clock edge
• Combinational logic
  • Computes next state
  • Computes outputs

FSM State Transition

• Moore FSM
  • Outputs labeled in each state
• Mealy FSM
  • Arcs indicate input/output

*Choice of machine: when do you want the output to change?

State Transition Diagram

State Transition Table, Next State Logic, Output Table, & Output Logic

Schematic

Timing Diagram

FSM State Encoding

• Binary encoding
• One-hot encoding
  • More flip-flops
  • Next state & output logic simpler

Factoring State Machine

FSM Design Procedure

1. Identify inputs & outputs
2. State transition diagram
3. State transition table
4. State encodings
5. Rewrite state transition table with encodings
6. Output table
7. Next state & output logic
8. Circuit schematic