文档介绍：Synchronous Sequential Circuit
Chapter 5
counter
Universal model
System output Variables
O0
Om
Er
Excitation Variables
E0
Combinational logic
System Input Variables
I0
In
S0
Sx
State Variables
Memory
Flip-flops
CLOCK
Modulo-n synchronous counter
A synchronous modulo-6 counter
The counter is to count up or down, in binary, depending on the value of a mode control input signal m. when m=1, the counter is to counter up; when m=0, the counter is to counter down.
The counter is to repeat or cycle.
Solution
Develop the state diagram.
Develop the state table.
Determine the number of state variables.
Assign the binary code to each state
Construct the transition table using the flip-flop excitation table.
Modulo-n synchronous counter
Develop state diagram
Develop state table
Modulo-n synchronous counter
A
B
C
D
E
F
m
m
m
m
m
m
m’
m’
m’
m’
m’
m’
A
B
C
D
E
F
F
A
B
C
D
E
B
C
D
E
F
A
m=0 m=1
Present state
Next state
Determine the number of State variables
2n-1<states<=2n
States=6
n=3
Assign the unique binary code to each state
Y3Y2Y1
A=000; B=001; C=010; D=011; E=100; F=101
Modulo-n synchronous counter
Construct transition table
Modulo-n synchronous counter
m=0 m=1
Present state
Next state
0
0
1
1
0
0
Y3 Y2 Y1
0
0
0
0
1
1
0
1
0
1
0
1
0
0
0
1
1
0
Y3 Y2 Y1
1
0
0
0
0
1
1
0
1
0
1
0
0
1
1
0
0
0
Y3 Y2 Y1
0
0
0
1
1
0
1
0
1
0
1
0
0
0
1
1
0
1
0
1
0
1
1
0
Qn Qn+1 T
Construct transition table
Modulo-n synchronous counter
m=0 m=1
Present state
Next state
0
0
1
1
0
0
Y3 Y2 Y1
0
0
0
0
1
1
0
1
0
1
0
1
0
0
0
1
1
0
Y3 (T3) Y2 Y1
1
0
0
0
0
1
1
0
1
0
1
0
0
1
1
0
0
0
Y3(T3) Y2 Y1
0
0
0
1
1
0
1
0
1
0
1
0
0
0
1
1
0
1
0
1
0
1
1
0
Qn Qn+1 T
1
0
0
0
1
0
0
0
0
1
0
1
Modulo-n synchronous counter
0
0
1
1
0
1
0
1
0
1
1
0
Qn Qn+1 T
Y3 Y2 Y1
001100
000011
010101
001010
T3 T2 T1
100010
11111