Rockwell SoniCrafter BT8960 - Manual (Page 35)

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2.0 Functional Description
2.2 Receive Section
Bt8960
Single-Chip 2B1Q Transceiver
N8960DSB
2.2.6.2 Peak Detector
(PKD)
The PKD is only used during the two-level transmission part of startup. It oper-
ates on the echo-free signal. A signal is detected to be a +3, if it is higher than
both of its neighbors, or a –3, if it is lower than both of its neighbors. If neither of
the peaked conditions exists, the output of the slicer is used.
2.2.6.3 Error Signals The detector computes two error signals for use in the equalizer: a 16-bit slicer
and a 16-bit equalizer.
2.2.6.4 Scrambler
Module
The scrambler may operate as either a scrambler or as a descrambler. The scram-
bler block is used during the scrambled-ones part of the startup sequence. This
provides an error-free signal for equalizer adaptation. This scrambler is essen-
tially a 23-bit-long LFSR with feedback. The feedback point depends on whether
the transceiver is being used in a central-office or remote-terminal application.
When operating as a descrambler, the input source is the detector output. The
symbol is converted to a bit stream, as shown in Table 2-4 for the two-level case.
The symbol is converted to a bit stream, as shown in Table 2-5 for the four-
level case.
Table 2-4. Two-Level Symbol-to-Bit Conversion
Input Symbol Output Bit
–3 0
+3 1
Table 2-5. Four-Level Symbol-to-Bit Conversion
Input Symbol
First Output Bit
(sign)
Second Output Bit
(magnitude)
–3 0 0
–1 0 1
+1 1 1
+3 1 0