bt8970 Mindspeed Technologies, bt8970 Datasheet - Page 50

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

4.0 Register
0x07—Receive Phase Select Register (receive_phase_select)
rphs[3:0]
0x08—Linear Echo Canceller Modes Register (linear_ec_modes)
enable_dc_tap
adapt_coefficents
zero_coefficients
zero_output
adapt_gain[1,0]
4-6
7
–
7
–
Receive Phase Select—Read/write binary field that defines the relative phase relationship
between QCLK and the sampling point of the ADC. The rising edges of QCLK corresponds to
the ADC sampling point when rphs = 0000. Each binary increment of rphs represents a
one-sixteenth QCLK period delay in the sampling point relative to QCLK.
Enable DC Tap—Read/write control bit which, when set, forces a constant +1 value into the
last data tap of the Linear Echo Canceler (LEC). This condition enables cancellation of any
residual DC offset present at the input to the LEC. When cleared, the last data tap operates
normally, as the oldest transmit data sample.
Adapt Coefficients—Read/write control bit which enables coefficient adaptation when set;
disables/freezes adaptation when cleared. Coefficient values are preserved when adaptation is
disabled.
Zero Coefficients—Read/write control bit that continuously zeros all coefficients when set;
allows normal coefficient updates, if enabled, when cleared. This behavior differs slightly from
the similar function (zero_coefficients) of the FFE and EP filters.
Zero Output—Read/write control bit which, when set, zeros the echo replica before
subtraction from the input signal. Achieves the affect of disabling or bypassing the echo
cancellation function. Does not disable coefficient adaptation. When cleared, normal echo
canceller operation is performed.
Adaptation Gain—Read/write binary field which specifies the adaptation gain.
6
6
–
–
Preliminary Information/Conexant Proprietary and Confidential
enable_dc_tap
adapt_gain[1,0]
5
–
5
00
01
10
11
coefficients
adapt_
4
4
–
Conexant
zero_coefficients
rphs[3]
3
3
zero_output
rphs[2]
2
2
Normalized Gain
Single-Chip HDSL Transceiver
512
adapt_gain[1]
64
1
4
rphs[1]
1
1
adapt_gain[0]
rphs[0]
100101B
Bt8970
0
0