Synchronous Sequential
Networks
Sequential Network Model
Clocked Synchronous
Sequential Network
Mealy Model
Outputs are only a function of the external inputs
and the present state
Z = g(X,Q)
Mealy model of a clocked synchronous sequential network.
Figure 7.3
Moore Model
Outputs are only a function of the present state
Z = g(Q)
Moore model of a clocked synchronous sequential network.
Figure 7.4
Analysis of Clocked Synchronous
Sequential Networks
•
•
•
•
•
•
•
Excitation and Output Expressions
Transition Equations
Transition Tables
Excitation Tables
State Tables
State Diagrams
Network Terminal Behavior
Logic diagram for Example 7.1
Figure 7.5
Logic diagram for Example 7.2
Figure 7.6
Excitation and Output
Expressions
• From example 7.1
D1  xQ2  Q1Q2
(7.4)
D2  xQ1  Q1Q2(7.5)
z  xQ1  xQ1 Q2
(7.6)
• From example 7.2
J1  y

J2  xQ1  xyQ1
z1  Q1Q2

(7.7)
K1  y  xQ2
(7.8)
(7.9)
K 2  x y  yQ1
(7.10)
(7.11)

z 2  Q1  Q2
(7.12)
Transition Equations
• From example 7.1

1
Q  xQ2  Q1Q2

Q2  xQ1  Q1Q2
(7.13)
(7.14)
• From example 7.2




Q1  yQ1  x yQ1  yQ1Q2
(7.15)
Q2  xQ1Q2  xyQ1Q2  xyQ2  xQ1Q2  yQ1Q2 (7.16)

Transition Table
Present state
(Q1Q2)
Next state
(Q1+Q2+)
Output
(z)
00
01
10
11
Input (x)
0
1
10
01
11
11
10
00
00
00
Input (x)
0
1
0
1
0
0
1
0
1
0
Example 7.1
Transition Table
Present state
(Q1Q2)
Next state
(Q1+Q2+)
00
01
10
11
Input (xy)
01
10
10
01
11
00
01
00
00
10
00
00
01
10
11
Example 7.2
Output
(z1z2)
11
11
11
00
00
01
00
11
01
Excitation Table
Present state
(Q1Q2)
Excitation
(D1D2)
Output
(z)
00
01
10
11
Input (x)
0
1
10
01
11
11
10
00
00
00
Input (x)
0
1
0
1
0
0
1
0
1
0
Example 7.1
Excitation Table
Present state
(Q1Q2)
Excitation
(J1K1,J2K2)
00
01
10
11
Input (xy)
01
10
11,00 01,11
11,00 00,11
11,11 01,01
11,11 00,01
00
00,00
00,00
00,00
00,00
Example 7.2
Output
(z1z2)
11
11,10
11,10
11,01
11,01
01
00
11
01
State Table
Present state
Next state
Output (z)
00A
01B
10C
11D
Input (x)
0
1
C
B
D
D
C
A
A
A
Input (x)
0
1
0
1
0
0
1
0
1
0
Example 7.1
State Table
Present state
Next state, Output (z)
Input (x)
A
B
C
D
0
C,0
D,0
C,1
A,1
Example 7.1
1
B,1
D,0
A,0
A,0
State Table
Present state
Next state
00A
01B
10C
11D
Input (xy)
01
10
C
B
D
A
B
A
A
C
00
A
B
C
D
Example 7.2
Output
(z1z2)
11
D
D
A
A
01
00
11
01
State diagram for Example 7.1
Figure 7.7
State diagram for Example 7.2
Figure 7.8
Timing diagram for Example 7.1
Figure 7.9
The analysis procedure
Figure 7.10
Modeling Clocked Synchronous
Sequential Network Behavior
•
•
•
•
•
•
State diagram
State Table
State Table Reduction: Implication table
Transition table: State Assignment
Excitation Table
Logic Diagram
The serial binary adder
Figure 7.11
State diagram for a Mealy serial binary adder
(a) Partial state diagram
(b) Completed state diagram
Figure 7.12
State diagram for a Moore serial binary adder
Figure 7.13
A sequence recognizer
Figure 7.14
State diagram for a sequence recognizer
Figure 7.15
A 0110/1001 sequence recognizer
Figure 7.16
State diagram for the final example
Figure 7.17
Experiment for determining equivalent pairs of states
Figure 7.18
The structure of an implication table
Figure 7.19
Implication table for determining the equivalent states
of Table 7.13
Figure 7.20
Implication table for determining equivalent states of
the 0110/1001 sequence recognizer
(a) Initial table
(b) Final table
Figure 7.21
Next-state and output Karnaugh maps for the transition
table of Table 7.17b
Figure 7.22
A state-assignment map for the state table of
Table 7.17a
Figure 7.23
Guidelines for Obtaining State
Assignments
Rule I:
Rule II:
Rule III:
Two or more present states that have the same
next state for a given input combination should
be made adjacent
For any present state and two adjacent input
combinations, the two next states should be
made adjacent
Two or more present states that produce the
same output symbol (0 or 1) for a given input
combination should be made adjacent (only
apply to one of the output symbols)
Next-state and output Karnaugh maps for the transition
table of Table 7.17c
Figure 7.24
Two approaches to handling unused states. (a) State
table. (b) Transition table with don’t-cares for unused
states. (c) Next-state maps, output map, and
expressions for table of Fig. 7.25b
Figure 7.25
(d) Transition table when unused states cause the network
to go to state A. (e) Next-state maps, output map, and
expressions for table of Fig. 7.25d
Figure 7.25 cont.
Logic diagram for the excitation table of Table 7.19
Figure 7.26
Excitation and output maps for the excitation table of
Table 7.20
Figure 7.27
Logic diagram for the excitation table of Table 7.20
Figure 7.28
Excitation and output maps for the Moore
serial binary adder
Figure 7.29
Logic diagram for the Moore serial binary adder
Figure 7.30
General structure of a clocked sequential network
realization using a PLD and clocked D flip-flops
Figure 7.31
A clocked synchronous sequential network realization
using a PLA and clocked D flip-flops
Figure 7.32