User`s guide

FFT
5-177
Description of Bit-Reversed Ordering. Two numbers are bit-reversed values of each
other when the binary representation of one is the mirror image of the binary
representation of the other. For example, in a three-bit system, one and four
are bit-reversed values of each other, since the three-bit binary representation
of one, 001, is the mirror image of the three-bit binary representation of four,
100.
The sequence 0, 1, 2, 3, 4, 5, 6, 7, is in linear order. To put the sequence in
bit-reversed order, replace each element in the linearly ordered sequence with
its bit-reversed counterpart. You can do this by translating the sequence into
its binary representation (with the minimum number of bits), then finding the
mirror image of each binary entry, and translating the sequence back to its
decimal representation. The resulting sequence is the original linearly ordered
sequence in bit-reversed order.
Selecting the Twiddle Factor Computation Method
The Twiddle factor computation parameter determines how the block
computes the necessary sine and cosine terms to calculate the term
0
1
2
3
4
5
6
7
0
4
2
6
1
5
3
7
Find mirror image of each entry
Translate to
binary
representation
Translate back
to decimal
representation
000
001
010
011
100
101
110
111
000
100
010
110
001
101
011
111
Linear Order
Bit-Reversed Order
(In a three-bit system)