Rockwell SoniCrafter BT8960 - Manual (Page 65)

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3.0 Registers
3.1 Conventions
Bt8960
Single-Chip 2B1Q Transceiver
N8960DSB
3.2.26 0x21—ADC Control Register (adc_control)
loop_back[1,0] Loopback Control—Read/write binary field specifying 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, back into the differential receiver balance inputs
(RXBP, RXBN). During silent loop back, the transmitter is turned off, and 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[2:0] Gain Control—Read/write binary field specifies the gain of the VGA.
7 6 5 4 3 2 1 0
– – loop_back[1] loop_back[0] – gain[2] gain[1] gain[0]
loop_back[1,0] Function
00 Normal Operation (Loop Back Disabled)
01 Hybrid Inputs Disabled (RXBP, RXBN)
10 Transmitting Loopback
11 Silent Loop Back
gain[2:0] VGA Gain
000 0dB
001 3 dB
010 6 dB
011 9 dB
100 12 dB
101 15 dB
110 15 dB
111 15 dB