Presentation on A2 Finite State machines

1. Finite State Machines

2. AS and A2 compared
• AS Revision
– Finite state machines with output
• Mealy machines
– Finite state machines without outputs
– State Transition Tables
– Decision tables

3. A2 new topics
– State Transition Diagrams
– Finite state machines with output
• Mealy and Moore machines
– Finite State Automata
• Deterministic FSAs (DFAs)
• Non-Deterministic FSAs (NFAs)

4. Revision: Mealy Machines
Output on Transition
• Using Boole Deusto
• First task – ballpoint
pen.
• Two states, retracted
and extended. Input
is either a click (1) or
fumble (0). Output is Transition table for ballpoint
ready to write (1) or pen
not ready to write (0) Current R R E E
Input 1 0 1 0
Next E R R E
Output 1 0 0 0

5. Challenge
• Using Boole Deusto or JFLAP:
• Create a machine that outputs 0 unless
it sees the sequence 111, in which
case it outputs a single 1.
• Create a vending machine which takes
either 5p or 10p and gives 15p sweets
plus change.

6. Revision – FSMs without outputs
• Ultra-Basic combination
lock.
• Two digit code ‘20’
• Numbers 012
• Start State
• Accepting State Decision Table
First is 2 Y Y N N
• Use software VAS Second is 0 Y N Y N
Output Pass Y N N N

7. Revision – FSMs without outputs
• Ultra-Basic combination
lock.
• Two digit code ‘20’
• Numbers 012
• Start State
• Accepting State Decision Table
First is 2 Y Y N N
• Use software VAS Second is 0 Y N Y N
Output Pass Y N N N