ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 81
Lecture Note #8 Finite State Machine
•
Analysis of sequential circuit
54
– Mealy and Moore machine
– Reverse engineering
» From schematics to statetransition diagram
•
Design of sequential circuit
57
– Design procedure
» 7 steps from specifications to the schematics
•
State reduction and assignment
56
– Two most important design steps
•
Reading Assignments:
– Section 54, 56, 57
ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 82
Finite State Machine and Sequential Logic
•
Sequential logic and Finitestate machine (FSM)
– FSM is a more general term of sequential logic
•
Storage register
– Multiple flipflops (finite states) in parallel
– No nextstate and output logic
•
Shift register
– Multiple flipflops (finite states) in series
– Might or might not have nextstate and output logic
•
Conversion of flipflop
– One flipflop, one nextstate logic, no output logic
Nextstate
Combinational
Circuit
Output
Combinational
Circuit
Finite
States
Inputs
Outputs
Feedbacks
Clocks
ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 83
Finitestate Machine and Counters
Nextstate
Combinational
Circuit
Finite
States
Outputs = states
Feedbacks
Clocks
•
Counter has no output logic
– The current states are the outputs
– Johnson and ring counters have even no nextstate logic
•
Counter has no data inputs, but only clock input
– Proceed through a welldefined sequence of states
– No data input to alter the sequence of states
•
Design of counter
– Selection of flipflops
– Design of nextstate logic
ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 84
Counter Design Procedure
•
Understand the problem
– Statetransition diagram and table
–
(States are outputs)
•
Selection of flipflops
– T, D and JK flipflops
•
Design of nextstate logic
– Truth table
» inputs are current states
•
(no data inputs)
» outputs are inputs to the flipflops
» derived by excitation table
•
(no output logic)
• Implementation
– Gate counts
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 85
FSM Design Procedure
•
Understand the problem
– Statetransition diagram and table
•
Number of states could be reduced (State Reduction)
– few states imply few flipflops
•
Assign binary values to states (State Assignment)
– can lead to few gate count in nextstate and output logic
•
Selection of flipflops
– T, D and JK flipflops
•
Design of nextstate logic
– inputs are current states and
data inputs
– outputs are inputs to the flipflops
•
Design of output logic
– Truth table is available for the specifications
• Implementation
ELEC151 Digital Circuits and Systems
HoChi Huang, Lecture Notes, No. 86
6 Basic Design Steps of FSM
• 1.
Understand the statement of the Specification
– With a block diagram
• 2.
Obtain an abstract specification of the FSM
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '11
 Prof.ShenghuiSong
 Digital circuits, HoChi Huang

Click to edit the document details