Graphics Programs Reference
In-Depth Information
The feedback connections associated with a shift register generator deter-
mine whether the output sequence will be maximal or not. For a given size
shift register, only few feedback connections lead to maximal sequence out-
puts. In order to illustrate this concept, consider the two 5-stage shift register
generators shown in
Fig. 4.21
. The shift register generator shown in Fig. 4.21a
generates a maximal length sequence, as clearly depicted by its state diagram.
However, the shift register generator shown in Fig. 4.21b produces three non-
maximal length sequences (depending on the initial state).
Σ
12345
10000
00001
01000
1
16
8
4
18
9
20
26
13
6
19
25
start
29
27
22
12
24
17
3
7
15
31
30
28
14
23
11
21
10
5
2
L
=
31
(a)
Σ
12345
L
=
3
27
13
22
start
00001
00001
1
1
16
16
8
8
4
4
2
2
17
17
24
24
12
12
6
6
19
19
9
9
20
20
start
start
3
3
7
7
15
15
31
31
30
30
29
29
26
26
21
21
10
10
L
=
21
L
=
7
14
23
11
5
18
25
28
start
(b)
Figure 4.21. (a) A 5-stage shift register generator. (b) Non-maximal length
5 stage shift register generator.
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