L64704 LSI Logic Corporation, L64704 Datasheet - Page 135

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

Figure 6.2
Viterbi Decoder
Synchronization
Decoder Data
Bit Count
3
3
Q-Channel
I-Channel
The decoder then proceeds to adjust either the phase in the phase rota-
tion module or the data stream alignment in the depuncturing logic by
successively stepping through as many combinations as needed (and
possibly all combinations) until synchronization is achieved. Because
both I and Q channels can appear inverted and swapped, four phases
are possible for the phase rotation block. Depending on the Viterbi code
rate chosen, the depuncturing mechanism includes up to two states.
(The 180 degree rotation is removed in the Reed-Solomon decoder
Viterbi Decoder Synchronization
Max Data
Bit Count
(VMDC1)
Rotation
Phase
Decision Logic
Rotate
Phase
In-Sync/Out-of-Sync
Max Bit Error
(VMBEC)
Count
Sync
Depuncturing
Logic
Configuration Register
Bit Error
Count
Decoded Data
Decoder
Viterbi
6-3