FSM and ASM
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The document discusses finite state machines (FSMs) and algorithmic state machines (ASMs). FSMs have a fixed set of states and can only be in one state at a time. ASMs provide a flowchart-like diagram representation of FSMs and are suitable for more complex FSMs with many inputs and outputs. ASMs have three main building blocks - state boxes, decision boxes, and conditional output boxes. State boxes represent states, decision boxes represent condition expressions, and conditional output boxes represent Mealy-type outputs that depend on state and inputs. The document provides examples of converting state diagrams to ASM charts and vice versa.
FSM and ASM
- 1. FSM and ASM Charts 1 o FINITE STATE MACHINE o ALGORITHMIC STATE MACHINE BY UNSA SHAKIR
- 2. Finite State Machine •A finite-state machine (FSM) or finite-state automaton is a mathematical model of computation. • We have a fixed set of states that the machine can be in •The machine can only be in one state at a time •A sequence of inputs is sent to the machine •Every state has a set of transitions and every transition is associated with an input and pointing to a state
- 3. ASM (algorithmic state machine) – Flowchart-like diagram – Algorithmic State Machine are suitable for FSMs with a larger number of inputs and outputs compared to FSMs expressed using state diagrams and state tables. – Provide the same information as an FSM – More descriptive, better for complex description – algorithm = sequencing + data manipulation – Algorithmic state machines can model both Mealy and Moore Finite State Machines
- 4. Algorithmic StateMachines 4 • ASMs have three types of building blocks: – State Box – Decision Box – Conditional Output Box
- 7. State Box • Indicated with a rectangle • Equivalent to a node in the State diagram • The name of the state is written outside the box • Moore-type outputs are written inside the box • Only the output that must be set to 1 is written (by default, if an output is not listed it is set to 0)
- 9. Decision Box • Indicated with a diamond shape • Used for a condition expression that must be tested • The exit path is chosen based on the outcome of the test • The condition is on one or more inputs to the FSM • Shortcut notation: w means “is w equal to 1?”
- 11. Conditional Output Box • Indicated with an oval shape • Used for a Mealy-type output signals • Not used for a Moore-type output signals • The outputs depend on the state variables and inputs • The condition that determines when such outputs are generated is placed in a separate decision box • It is mostly use for high (1) output state.
- 15. • Incorrect ASM charts:
- 17. State diagram and ASM chart conversion
- 18. State diagram and ASM chart conversion
- 21. ASM Chart for Moore FSM – Example 1
- 22. A w 0= z 0= w 1= z 1=Bw 0= z 0= Reset w 1= z 0= Mealy State diagram Example 2
- 23. ASM Chart for Mealy FSM – Example 2
- 24. State diagram C z 1= Reset B z 0=A z 0=w 0= w 1= w 1= w 0= w 0= w 1= Example 3
- 25. Present Next state Output state w = 0 w = 1 z A A B 0 B A C 0 C A C 1 State table Example 3
- 31. practice • Design an FSM that detects if the previous two values of the input w were equal to 00 or 11 • If either condition is true then the output z should be set to 1; otherwise to 0. • Implement this as a Mealy-type machine