GDC21D003 Datasheet, PDF (45/77 Pages) Hynix Semiconductor – VSB Receiver

6.3.8 Field Sync Recovery
Transmitter inserts 1 Data Segment long Field Sync
every 313^th segment. Inserted Field Sync structure
is described in Figure 6.3.13. Field Sync is found
GDC21D003
using PN511 as shown in Figure 6.3.13. Cause
pattern of PN511 input from transmitter is already
acknowledged, by comparing with transmitted
signal, the interval having the most similar pattern
is acknowledged as Field Sync interval.
Segment
sync
(4 symbols)
PN511
(511 symbols)
PN63
PN63*
PN63
VSB mode
reserved ^{12 symbol}
(63 symbols) (63 symbols) (63 symbols) (24 symbols) (92 symbols)
data
(12 symbols)
Figure 6.3.13 Field Sync Structure
Among three PN63 signals exceptionally the
second one changes its polarity in every Field.
Equalizer uses this data interval, so polarity
information(FOE : pin number 66) should be
detected. This polarity information detection starts
after finding Field Sync. Used algorithm is similar
to that of Field Sync case. If the second PN63
phase is the same as others, FOE signal outputs ‘0’,
otherwise it outputs ‘1’.
Error
Calculation
Minimum
Error
Detection
Confidence
Counter
nSyncLock
nFsync
nFldLock
Reference
Generation
Polarity
Error
Detection
Foe
nFrmLock
Figure 6.3.14 The Block Diagram of Field Sync Recovery
Figure 6.3.14 is the block diagram of Field Sync
Recovery. Input signal calculates error value by the
Data Segment, comparing with Reference
Generation output. Among these error values, the
smallest Data Segment is acknowledged as Field
Sync interval, Confidence Counter checks its
confidence and generates Field Sync. And after
finding Field Sync it detects Polarity Error of the
second PN63 interval in Error Calculation output
and generates Foe signal.
Field Sync Recovery generates nVSBmodstart(in
I²C bus register8) and nSyncLock(in I²C bus
register8) signal. nVSBmodstart signal is used as
initialization signal of VSB Mode Detect block.
When this signal is ‘1’, it means the initialization
state, when it is ‘0’, it means the operation state.
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