Hardware Reference
In-Depth Information
a
I
1
O
1
I
2
M
A
V
M
B
V
U
O
2
I
2
M
B
b
I
1
I
1
M
A
U
M
A
V
U
O
1
I
2
O
2
M
B
Fig. 5.1
Networks
N
0
obtained by series composition of driving machine
N
D
M
A
$
M
B
with
M
B
or M
A
.(
a
) The series topology .M
A
M
B
/
#
I
1
I
2
U
O
1
!
M
B
is used to compute the input
don't care sequences of M
B
;(
b
) The series topology .M
A
M
B
/
#
I
1
I
2
V
O
2
!
M
A
is used to
compute the input don't care sequences of M
A
1. The series topology .M
A
M
B
/
#
I
1
I
2
V
O
2
!
M
B
preserves the input don't
care sequences of M
B
.
2. The series topology .M
A
M
B
/
#
I
1
I
2
U
O
1
!
M
A
preserves the input don't
care sequences of M
A
.
Example 5.1.
Figure
5.2
shows a series topology M
A
!
M
B
and the computation
of the input don't care sequences with the procedure by Kim and Newborn,
providing the full flexibility at M
B
. Notice that M
B
can be reduced to two states
(by merging states 22, 33 and 3T ), whereas M
B
has three states.
The theory of input don't care sequences was developed independently in the
Soviet Union by Yevtushenko [152].
Another approach based on injecting faults into the component FSM M
B
and
checking whether the injected fault is redundant was proposed by Ferrandi et al. in
[40]. This method does not compute the complete flexibility, but the experiments
reported show that the computed partial flexibility is sufficient to achieve a good
optimization of M
B
.
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