bt8970 Mindspeed Technologies, bt8970 Datasheet - Page 56

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

4.0 Register
0x20—Test Register (reserved9)
A 1-byte read/write register used for device testing by Rockwell. This register is automatically initialized to
0x00 upon RST assertion and initial power application. This register must be initialized according to the device
driver provided by Rockwell.
0x21—ADC Control Register (adc_control)
loop_back[1,0]
gain[2:0]
4-12
7
–
Loopback Control—Read/write binary field specifies if loopback is enabled, and the type of
loopback that is enabled. During transmitting loopback, the differential receiver inputs (RXP,
RXN) are disabled. The loopback path is intended to go from the transmitter outputs (TXP,
TXN) through the external hybrid circuit and back into the differential receiver balance inputs
(RXBP, RXBN). During silent loopback, the transmitter is turned off.The output of the
pulse-shaping filter in the transmit section is internally connected to the input of the ADC in
the receive section.
Gain Control—Read/write binary field specifies the gain of the VGA.
6
–
Preliminary Information/Conexant Proprietary and Confidential
loop_back[1,0]
loop_back[1]
gain[2:0]
5
000
001
010
011
100
101
110
111
00
01
10
11
loop_back[0]
4
Conexant
3
–
Normal Operation (Loopback Disabled)
Hybrid Inputs Disabled (RXBP, RXBN)
gain[2]
Transmitting Loopback
2
Silent Loopback
VGA Gain
Function
12 dB
15 dB
15 dB
15 dB
Single-Chip HDSL Transceiver
3 dB
6 dB
9 dB
0dB
gain[1]
1
gain[0]
100101B
Bt8970
0