Rockwell SoniCrafter BT8960 - Manual (Page 26)

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2.0 Functional Description
2.1 Transmit Section
Bt8960
Single-Chip 2B1Q Transceiver
N8960DSB
2.1.1 Symbol Source Selector/Scrambler
The input source selector/scrambler can be configured through the Transmitter
Modes Register [transmitter_modes; 0x0B] data_source [2:0] bits to select the
source of the data to be transmitted and determine whether or not the data is
scrambled. The symbol source selector/scrambler modes are specified in Table 2-
1.
Table 2-1. Symbol Source Selector/Scrambler Modes
data_source[2:0] Symbol Source Selector/Scrambler Mode
000 Isolated pulse. Level selected by isolated_pulse[1,0]. The meter timer must be enabled and in the con-
tinuous mode. The pulse repetition interval is determined by the meter-timer-countdown interval.
001 Four-level scrambled detector loopback. Sign and magnitude bits from the receiver detector are scram-
bled and looped back to the transmitter. Feedback polynomial determined by the htur_lfsr control bit.
010 Four-level unscrambled data. Transmits the four-level (2B1Q) sign and magnitude bits from the transmit
channel unit.
011 Four-level scrambled ones. Transmits a scrambled, constant high-logic level as a four-level (2B1Q) sig-
nal. Feedback polynomial determined by the htur_lfsr control bit.
100 Reserved.
101 Four-level scrambled data. Scrambles and transmits the four-level (2B1Q) sign and magnitude bits from
the channel unit transmit interface. Feedback polynomial determined by the htur_lfsr control bit.
110 Two-level unscrambled data. Constantly forces the magnitude bit from the transmit channel unit inter-
face to a logic zero, and transmits the resulting two-level signal (as determined by the sign bit) without
scrambling. Valid output levels limited to +3, –3.
111 Two-level scrambled ones. Transmits a scrambled, constant high-logic level, as a two-level signal. Feed-
back polynomial determined by the htur_lfsr control bit. Scrambler is run at the symbol rate (half-bit
rate) to produce the sign bit of the transmitted signal while the magnitude bit is sourced with a constant
logic zero. Valid output levels limited to +3, –3.