msm7731-01 Oki Semiconductor, msm7731-01 Datasheet - Page 34

• Manufacturer Part Number: msm7731-01
• Description: Multifunction Pcm Codec Voice Signal Processor
• Manufacturer: Oki Semiconductor

¡ Semiconductor
(6) CR5 (Acoustic echo canceler settings)
B7 .......... "Through mode" control 1: "through mode", 0: normal mode (echo cnaceler operation)
B6, B5 ... Reserved bits
B4 .......... Howling detector control
B3 .......... Center clip control
B2 .......... Coefficient update control
B1 .......... Attenuator control
B0 .......... Gain controller
CR5
Initial value
This is the "through mode" control bit for the acoustic echo canceler. In the
"through mode", RinA and SinA data is output directly to RoutA and SoutA
respectively. Coefficients are not reset.
This bit is internally ORed with the ATHR pin.
This bit controls the function to detect and cancel the howling that occurs in an
acoustic system such as a handsfree communication system.
This bit is internally ORed with the AHD pin.
When the SoutA output of the acoustic echo canceler is –57 dBm0 or less, the
center clip function forcibly sets it to the minimum positive value.
This bit selects whether the adaptive FIR filter (AFR) coefficients for the
acoustic echo canceler will be updated.
This bit is internally ORed with the AHLD pin.
This bit turns ON or OFF the ATT function to prevent howling by means of
attenuators (ATTsA, ATTrA) provided in the RinA input and SoutA output of
the acoustic echo canceler.
If input is only to RinA, the ATT for SoutA (ATTsA) is activated. If input is only
to SinA, or if there is input to both SinA and RinA, the ATT for RinA input
(ATTrA) is activated. The ATT value of each attenuator is approximately 6 dB.
This bit is internally ORed with the AATT pin.
This bit turns ON or OFF the gain control function to control the RinA input
level and prevent howling by means of a gain controller (GainA) provided in
the RinA input of the acoustic echo canceler.
The gain controller adjusts the RIN input level when it is –10 dBm0 or above,
and it has the control range of 0 to –8.5 dB.
This bit is internally ORed with the AGC pin.
ATHR
B7
0
B6
—
0
B5
—
0
Modification of initial values is inhibited
1: OFF,
1: ON,
1: fixed coefficients,
1: ATT OFF,
1: GC OFF,
AHD
B4
0
ACLP
B3
0
AHLD
B2
0
0: ON
0: updated coefficients
0: ATT ON
0: OFF
0: GC ON
AATT
B1
0
MSM7731-01
AGC
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B0
0