bt8970 Mindspeed Technologies, bt8970 Datasheet - Page 63

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

Bt8970
Single-Chip HDSL Transceiver
0x3C—Digital AGC Modes Register (dagc_modes)
eq_error_
adaptation
adapt_coefficient
adapt_gain
0x3D—Feed Forward Equalizer Modes Register (ffe_modes)
adapt_last_coeff
zero_coefficients
adapt_coefficents
adapt_gain
100101B
7
–
7
–
Equalizer Error Adaptation—Read/write control bit that selects between the equalizer-error
adaptation mode when set, and the self-adaptation mode when cleared. Equalizer error
adaptation uses the equalizer error signal produced by the slicer as the DAGC error input
signal. In self adaptation, the value of the DAGC Target Register [dagc_target_low,
dagc_target_high; 0x38–0x39] is subtracted from the absolute value of the receive signal at the
output of the DAGC, and this difference is used as the error input signal.
Adapt Coefficients—Read/write control bit that enables coefficient adaptation when set;
disables/freezes adaptation when cleared. Coefficient values are preserved when adaptation is
disabled.
Adaptation Gain—Read/write control bit that specifies the adaptation gain. When set, the
adaptation gain is eight times higher than when cleared.
Adapt Last Coefficient—Read/write control bit enables adaptation of the last (oldest)
coefficient only when set; allows all coefficient adaptation when cleared. Overall coefficient
adaptation must be enabled (adapt_coefficients = 1) for this behavior to occur. If coefficient
adaptation is disabled (adapt_coefficients = 0), the value of this control bit is not used.
Zero Coefficients—Read/write control bit which, with coefficient adaptation enabled
(adapt_coefficients = 1), continuously zeros all coefficients when set; allows normal
coefficient updates when cleared. If coefficient adaptation is disabled (adapt_coefficients = 0),
this control bit has no affect. This behavior differs slightly from the similar function
(zero_coefficients) of the LEC, NEC, and DFE filters.
Adapt Coefficients—Read/write control bit enables coefficient adaptation when set;
disables/freezes adaptation when cleared. Coefficient values are preserved when adaptation is
disabled. This overall coefficient adaptation must be enabled for adapt_last_coeff to have an
affect.
Adaptation Gain—Read/write control bit specifies the adaptation gain. When set, the
adaptation gain is four times higher than when cleared.
6
6
–
–
Preliminary Information/Conexant Proprietary and Confidential
5
–
5
–
4
4
–
–
Conexant
adapt_last_coeff zero_coefficents
3
–
3
adaptation
eq_error_
2
2
adapt_coefficient
coefficents
adapt_
1
1
4.0 Register
adapt_gain
adapt_gain
0
0
4-19