bt8970 Mindspeed Technologies, bt8970 Datasheet - Page 20

• Manufacturer Part Number: bt8970
• Description: Single-chip Hdsl Transceiver
• Manufacturer: Mindspeed Technologies

2.0 Functional Description
2.1 Transmit Section
Table 2-1. Symbol Source Selector/Scrambler Modes
Table 2-2. Four-Level Bit-to-Symbol Conversions
in
Table 2-3. Two-Level Bit-to-Symbol Conversions
2-2
data_source[2:0]
Table
The bit stream is converted into symbols for the four-level cases as shown in
In two-level mode, the magnitude bit is forced to a zero. This forces the symbols to be +3 and –3, as shown
2-3.
000
001
010
011
100
101
110
111
First Input Bit
First Input Bit
(sign)
(sign)
0
0
1
1
0
1
continuous mode. The pulse repetition interval is determined by the meter-timer-countdown interval.
scrambled and looped back to the transmitter. Feedback polynomial determined by the htur_lfsr control
bit.
transmit channel unit.
signal. Feedback polynomial determined by the htur_lfsr control bit.
the channel unit transmit interface. Feedback polynomial determined by the htur_lfsr control bit.
interface 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.
Feedback 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.
Isolated pulse. Level selected by isolated_pulse[1,0]. The meter timer must be enabled and in the
Four-level scrambled detector loopback. Sign and magnitude bits from the receiver detector are
Four-level unscrambled data. Transmits the four-level (2B1Q) sign and magnitude bits from the
Four-level scrambled ones. Transmits a scrambled, constant high-logic level as a four-level (2B1Q)
Reserved.
Four-level scrambled data. Scrambles and transmits the four-level (2B1Q) sign and magnitude bits from
Two-level unscrambled data. Constantly forces the magnitude bit from the transmit channel unit
Two-level scrambled ones. Transmits a scrambled, constant high-logic level, as a two-level signal.
Preliminary Information/Conexant Proprietary and Confidential
Second Input Bit (magnitude)
Second Input Bit (magnitude)
Symbol Source Selector/Scrambler Mode
Conexant
don’t care
don’t care
0
1
1
0
Table
Single-Chip HDSL Transceiver
Output Symbol
Output Symbol
2-2.
–3
–1
+1
+3
–3
+3
100101B
Bt8970