•
Outputs valid at following falling clock edge
Reset
AB =00
Z =0
X =1
AB =00
Z =0
X =0
AB =00
Z =0
X =1
AB =01
Z =0
X =1
AB =10
Z =1
X =0
AB =1
1
Z =1
X =1
AB =01
Z =0
X
Clk
A
B
Z
Reset'
100
Chapter 3: Short Review of Sequential Circuits
3-74

EE271 @ Thuy T. Le
SJSU - EE
Chapter 3: Short Review of Sequential Circuits
38
Partially completed State Transition Table
A
B
X
A+
B+
Z
0
0
0
0
1
0
1
0
0
0
0
1
0
?
?
?
1
1
1
0
1
0
0
?
?
?
1
0
1
1
1
1
0
1
0
1
1
?
?
?
K-maps for
A
+,
B
+, and
Z
are then developed
from completed Transition Table
Chapter 3: Short Review of Sequential Circuits
3-75
Formal Method
A+ = B
(
A + X
)
= AB + BX
B+ =
J
b
B' +
K
b
'
B =
(
A'
XOR
X
)
B' + XB = AB'X + A'B'X' + BX
Z
= AX + BX'
AB
X
00
01
11
10
0
0
0
1
0
1
0
1
1
0
A
+
AB
X
00
01
11
10
0
1
0
0
0
1
0
1
1
1
B
+
AB
X
00
01
11
10
0
0
1
1
0
1
0
0
1
1
Z
Can also be built
from Transition
Table developed by
Ad Hoc technique
Chapter 3: Short Review of Sequential Circuits
3-76

EE271 @ Thuy T. Le
SJSU - EE
Chapter 3: Short Review of Sequential Circuits
39
•
Some outputs in output boxes as well as state boxes
•
This is intrinsic in Mealy machine implementation
Complete Mealy ASM Chart
S
0
= 00, S
1
= 01, S
2
= 10, S
3
= 11
S
0
00
X
H. Z
01
10
X
H. Z
H. Z
11
X
X
0
1
0
0
1
1
0
1
S
1
S
2
S
3
Chapter 3: Short Review of Sequential Circuits
3-77
Finite State Machine Partitioning
Why partition?
Mapping FSM onto programmable logic components that:
Have limit number of input/output pins
Have limited number of product terms or other programmable
resources
Next states
and output
functions
10 inputs
7 outputs
Partition 1
Partition 2
7 inputs
6 inputs
10 inputs
4 outputs
3 outputs
Chapter 3: Short Review of Sequential Circuits
3-78