msm7575 Oki Semiconductor, msm7575 Datasheet - Page 8

• Manufacturer Part Number: msm7575
• Description: Multi-function Pcm Codec
• Manufacturer: Oki Semiconductor

¡ Semiconductor
VOXO
Transmit VOX function signal output.
VOX function is to recognize the presence or absence of the transmit voice signal by detecting the
signal energy. “H” and “L” levels set to this pin correspond to the presence and the absence,
respectively. This result appears also at the register data CR7-B7. The signal energy detect
threshold is set by the control register data CR6-B6, B5.
VOXI
Signal input for receive VOX function.
The “H” level at VOXI indicates the presence of voice signal, the decoder block processes normal
receive signal, and the voice signal appears at analog output pins . The “L” level indicates the
absence of voice signal, 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. Because this
signal is ORed with the register data CR6-B3, the control register data CR6-B3 should be set to
digital “0”.
Note: VOXO, VOXI function become valid when setting CR6-B7 to digital “1”.
Voice Output
VFRO
Voice Input
GSX2
VOXO
VOXI
(b) Receive VOX Function (CR6-B3: digital "0") Timing Diagram
Normal Voice Signal
Decoded Time period
T
Presence
Detect
VXON
(a) Transmit VOX Function Timing Diagram
(Presence)
(Presence)
Figure 4 VOX Function
Background
Noise
(Absence)
(Absence)
T
Absence
Detect (Hang-over time)
VXOFF
(Presence)
(Presence)
MSM7575
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