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in Fig-1 it is shown as Level-1. This is computed using the formula in Eqn-1
by assigning
L
1
.
1
in
1
=0
and L
1
.
1
in
2
= 0 since they are primary input nets. Hence
L
1
.
1
out
= 1. The same formula can be applied progressively to determine rest of
the levels.
a
sum
1.1
2.1
b
c
2.2
carry
3.1
1.2
Level-1
Level-2
Level-3
Fig. 1.
Group of gates leveled based on the circuit depth
3.2 Power Estimation Methodology
The proposed methodology estimates the maximum instantaneous power by de-
termining the maximum activity among the activity at each levels of the circuit.
Mathematically this can be expressed as follows.
P
peak
=
Max
(
A
l
)
(2)
where
P
peak
is the estimated worst peak power and
A
l
is the maximal activity
at
l
th
level of the circuit. Detail is explained in the following section, Section 4.
4 Background on Binary Integer Linear Program
Binary integer linear programing(BILP) is a class of optimization method called
linear programing(LP) method. In BILP the variables are constraint to take only
0 or 1 value-a binary digit. The BILP problem is to optimize a given function
called
objective function
subject to a given set of constraints. The general form
of BILP can be stated as follows:
Minimize
:
f
(
x
),
Subject to
:
Ax
=0,
x
[0
,
1]
In our earlier work[10] we have explored the BILP method to maximize the
toggle activity subject to functionality constraints. Summary of the method is
presented in Table 1.