Digital Electronics
This or that
Mealy or Moore? Four Quick Pairs
Do you know the difference? Four pairs, answer before I do
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Lesson notes
Model sequential behaviour with state diagrams and tell Mealy from Moore machines
Key points
- Mealy / Moore: Moore outputs depend only on current state; Mealy outputs depend on state and input.
- Characteristic / Excitation: Characteristic table gives next state from inputs and present state; excitation table gives inputs needed for a transition.
- Synchronous / Asynchronous: Synchronous counters share one clock; asynchronous ripple counters clock each stage from the previous one.
- Latch / Flip-flop: A latch is level-sensitive; a flip-flop is edge-triggered and changes only on the clock edge.
Takeaway: Moore: output from state only. Mealy: state plus input.
Quick check: In a 101 detector whose output is written inside the states, what type is it?
- Mealy machine
- Moore machine
- Combinational circuit
Outputs tied to states, not transitions, depend only on current state: Moore.
state diagramMealy machineMoore machine
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