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.

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

6. The StateBox
6

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)

8. The DecisionBox
Symbol
8
Alternate Symbol

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?”

10. The Conditional OutputBox
1
0

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.

12. talarico@gonzaga.edu 12

13. talarico@gonzaga.edu 13

14. Another Loopingexample
01
S0
X
CX
X
CX
01
S0
14

15. • Incorrect ASM charts:

16. correct ASM charts
16

17. State diagram and ASM chart conversion

18. State diagram and ASM chart conversion

19. State Diagram
Example 1

20. State Table
Example 1

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