CE6313 Datasheet, PDF (11/24 Pages) Intel Corporation – DVB-S Satellite Demodulator

VITERBI
Coarse
Bit
Error
Count
CE6313
Data Sheet
VIT_MAXERR[3:0]
0
0
Data Bits
Status
Figure 7 - Viterbi Error Count Coarse Indication
2.4.2 The Frame Alignment Block
The frame alignment algorithm detects a sequence of correctly spaced synchronizing bytes in the Viterbi decoded
bit-stream and arranges the input into blocks of data bytes. Each block consists of 204 bytes for DVB and 147 bytes
for DSS. In the DSS mode, the synchronizing byte is removed from the data stream, so only 146 bytes of a block
are passed to the next stage. The frame alignment block also removes the 180° phase ambiguity not removed by
the Viterbi decoder.
2.4.3 The De-Interleaver Block
2.4.3.1 DVB
Before transmission, the data bytes are interleaved with each other in a cyclic pattern of twelve. This ensures the
bytes are spaced out to avoid the possibility of a noise spike corrupting a group of consecutive message bytes.
Figure 8 below shows conceptually how the convolutional de-interleaving system works. The synchronization byte
is always loaded into the First-In-First-Out (FIFO) memory in branch 0. The switch is operated at regular byte
intervals to insert successively received bytes into successive branches. After 12 bytes have been received,
byte 13 is written next to the synchronization byte in branch 0, etc. In the CE6313, this de-interleaving function is
realized using on-chip Random Access Memory (RAM).
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Intel Corporation