msm7708-02 Oki Semiconductor, msm7708-02 Datasheet - Page 10

• Manufacturer Part Number: msm7708-02
• Description: Serial Register Interface Adpcm Codec For Telephone Recording
• Manufacturer: Oki Semiconductor

Input voice signal
GSX2
VOXO pin
VOXI pin
Regenerated voice
VFRO
¡ Semiconductor
VOXO
Transmit side voice/silence detect signal output.
This output is valid when CR6 - B7 is set to "1". VOXO shows the presence or absence of the
transmit voice signal by detecting the signal. "1" and "0" set to this pin correspond to the presence
and the absence, respectively. This result also appears at the register data CR7 - B7. The signal
detect threshold is set by the control register CR6 - B6, B5. When control register CR0 - B6 is set
to "1" and VOXI input is "1" during the voice detection (VOXO = "1"), receive signal is
automatically suppressed by 6 dB.
VOXI
Receive side voice/silence detect signal input.
This output is valid when CR6 - B7 is set to "1". A "1" level at VOXI indicates the presence of voice
signal, in which case the decoder block processes normal receive signal and the voice signal
appears at analog output pins. A "0" level indicates the absence of voice signal, in which case the
background noise generated in this device is transferred to the analog output pins. The
background noise amplitude is set by the control register CR6 - B1, B0. Since this signal is ORed
with the register CR6 - B3, set the control register CR6 - B3 to "0" when using this pin. When
control register CR0 - B6 is set to "1" and VOXI input is "1" during the voice detection (VOXO =
"1") receive signal is automatically suppressed by 6 dB.
Note:
pin
pin
The VOXO and VOXI pin functions are enabled when CR6 - B7 is set to "1".
Regenerated Voice Signal
Voice Detection Time
T
VXON
Generation Time
(a) Transmission Side Voice/Silence Detect Function Timing Diagram
(b) Receive Side Voice/Silence Detect Function Timing Diagram
Figure 2 Voice/Silence Detect Function
Voice
Voice
Noise Generation Time
Internal Background
Silence
Silence
Silence Detection Time
(Hangover Time) T
VXOFF
Voice
Voice
MSM7708-02
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