msm7719-01 Oki Semiconductor, msm7719-01 Datasheet - Page 14

• Manufacturer Part Number: msm7719-01
• Description: Echo Canceler With Adpcm Transcoder
• Manufacturer: Oki Semiconductor

¡ Semiconductor
VOXO
Signal outut for transmit side VOX function.
This pin is effective when CR6-B7 is set to logic “1” (VOX ON).
The VOX function recognizes the presence or absence of the transmit voice signal by detecting the
level of the transmit signal to the line echo canceler. “1” and “0” levels set to this pin correspond to
the presence and the absence of voice, respectively. This result appears also at the register bit CR7-
B7. The signal energy detect threshold is set by the control register bits CR6-B6, B5.
The timing diagram of the VOX function is shown in Figure 3.
The transmit signal to the line echo canceler refers to the signal input to the PCMLNI pin.
Refer to Figure 6.
VOXI
Signal input for receive side (acoustic echo canceler Sin side) VOX function.
The “1” level at VOXI indicates the presence of a voice signal, the decoder block processes normal
receive signal, and the voice signal on the PCMACI pin goes through. The “0” level indicates the
absence of a voice signal and the background noise generated in this device is output.
The background noise amplitude is set by the control register CR6.
Because this signal is ORed with the register bit CR6-B3, set CR6-B3 to logic “0” when using this
pin.
When this pin control is not used (i.e., when controlling by the control register), set this pin to logic
“0”.
Refer to Figure 6.
Transmit Signal
PCMLNI
(shown as an
analog signal)
Receive Signal
Acoustic Echo
Canceler Sin
(shown as an
analog signal)
VOXO
VOXI
T
Voice
Detect
VXON
Decoded Time Period
Receive Signal
Voice
Voice
(a) Transmit Side VOX Function Timing Diagram
(b) Receive Side VOX Function Timing Diagram
Figure 6 VOX Function
T
Silence
Detect (Hangover time)
Background
VXOFF
Silence
Noise
Silence
Voice
Voice
MSM7719-01
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