Depth 12 Interleaver/De-Interleaver; Figure A-18. Interleaver/De-Interleaver - Comtech EF Data SDM-9000 Installation And Operation Manual

SDM-9000 Satellite Modem
A.2.8 Depth 12 Interleaver/De-interleaver
Conceptually, the interleaver is composed of I = 12 branches, cyclically connected to the
input byte stream by the input switch. Each branch is a FIFO shift register, with
depth = 17 x branch index. The cells of the FIFO contain 1 byte, and the input and output
branches are synchronized. For synchronization purposes, the sync bytes and inverted
sync bytes are always routed in branch 0 of the interleaver, corresponding to a null delay.
The de-interleaver is similar in principle to the interleaver, but the branch indexes are
reversed (i.e., branch 0 corresponds to the longest delay). De-interleaver synchronization
is accomplished by routing the first recognized sync byte to branch 0.
Figure A-18 shows the interleaver/de-interleaver block diagram.
0
1
17
2
17x2
3
17x3
11
INTERLEAVER
Rev. 4
SYNC BYTE ROUTE
0
1
2
3
•
•
•
11
17x11
17 BYTE FIFO SHIFT REGISTER

Figure A-18. Interleaver/De-interleaver

SYNC BYTE ROUTE
0
17x11
•
•
•
8
17x3
9
17x2
10
17
11
DE-INTERLEAVER
Options
0
8
9
10
11
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