Sahithyan's S2 — Computer Organization and Digital Design
State Machines
Aka. finite state machines (FSMs). Used to model systems that move through a predetermined sequence of states based on inputs and current state.
Components
- A finite set of states
- A set of inputs
- A set of outputs
- A state transition function
- An output function
- An initial state
A basic state machine implementation requires:
- State registers to store the current state
- Combinational logic for:
- Next state logic (state transition function)
- Output logic
- Clock signal for synchronization
State Diagram Representation
State machines are commonly represented using state diagrams.
- Circles represent states
- Arrows show transitions between states
- Labels on arrows show input conditions
- Labels in circles (Moore) or on arrows (Mealy) show outputs
State Machine Design Process
- Define states and transitions
- Create state diagram
- Choose state encoding
- Design combinational logic
- Implement using flip-flops and gates
Implementation Considerations
When implementing state machines:
- Choose appropriate state encoding (binary, one-hot, etc.)
- Minimize number of states
- Handle unknown states
- Consider timing requirements
- Plan for testability
State machines are essential in sequential logic design, providing a structured approach to implementing complex digital systems with memory and control capabilities.