MSM7731-02 OKI [OKI electronic componets], MSM7731-02 Datasheet - Page 32

• Manufacturer Part Number: MSM7731-02
• Description: Dual Echo Canceler & Noise Canceler with Dual Codec for Hands-Free
• Manufacturer: OKI [OKI electronic componets]

(5) CR4 (Line echo canceler setting)
B7
B6
B5
B4
B3
B2
1 Semiconductor
Initial Value
CR4
NCPAD2
“Through mode” control
This is the “through mode” control bit for the line echo canceler. In the “through mode”, RinL and SinL
data is output directly to RoutL and SoutL respectively while each echo coefficient is maintained . In the
through mode, the functions of LHD, LHLD, LATT and LGC are invalid. Because data is read by this
bit in synchronization with the rising edge of the SYNC signal, hold the data in the bit for 250 s or
longer.
This bit is internally ORed with the LTHR pin.
Reserved bit.
Coefficient update control
This bit selects whether the adaptive FIR filter (AFR) coefficients for the line echo canceler will be
updated. This unction is valid when the ATHR pin is in the normal mode.
Because data is read into this bit by synchronization with the rising edge of the SYNC signal, hold the
data at the bit for 250 µs or longer.
Howling detector control
This bit controls the function to detect and cancel the howling that occurs in an acoustic system such as
a handsfree communication system. This function is valid when the LTHR pin is in the normal mode.
Because this bit is read in synchronization with the rising edge of the SYNC signal, hold the data in the
bit for 250 µs or longer.
This bit is internally ORed with the LHD pin.
Center clip control
When the SoutL output of the line echo canceler is –57 dBm0 or less, the center clip function forcibly
sets it to the minimum positive value. This function is valid when the LTHR pin is in the normal mode.
Because this bit is read in synchronization with the rising edge of the SYNC signal, hold the data in the
bit for 250 µs or longer.
NCPAD control
This bit adjusts the noise canceler I/O gain. The gain adjustment is valid for tone control after canceling
the noise. The bigger the input level of the noise canceler is, the better the sound quality is. Because this
bit is read in synchronization with the rising edge of the SYNC signal, hold the data in the bit for 250 µs
or longer. This bit is internally ORed with the NCPAD1 pin. (Refer to the NCPAD2 pin of CR5-B2.)
0
0
1
1
LTHR
B7
0
B6
—
0
NCPAD1
LHLD
0
1
0
1
1: “through mode” 0: normal mode (echo canceler operation)
Modification of initial values is inhibited.
1: fixed coefficients 0: updated coefficients
1: OFF
1: ON
B5
0
LHD
B4
0
GPADNC (dB)
0: ON
0: OFF
LCLP
B3
0
12
18
0
6
NCPAD1
B2
0
LATT
LPADNC (dB)
B1
0
FEDL7731-02-04
–12
–18
–6
MSM7731-02
0
LGC
B0
0
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