15
BL-C111A/BL-C131A
4.1.10. Privacy Mode Control Circuit
Privacy Mode is a function to protect privacy so that a lens may be concealed in a cover part by pushing the Privacy Mode
switch (SW801) and the picture may not be seen.
CPU detects condition of SW801.
4.1.11. Sound Block
Microphone(MIC851)
Input sound.
ALC Amplifier (IC852)
Power Supply: 3.3V
Amplifier for Auto Level Control
PCM Codec (IC851)
Power Supply Voltage: 3.3V
Clock Frequency: Contains a built-in PLL function and generates a clock from the BCLK (256 KHz).
Contains an amplifier, LPF, gain adjustment, AD/DA converter, host I/F, PCM serial I/F and speaker output function.
Flow of Sound Signal
[Microphone sound]
1. The sound data input from pin 1 of the microphone is amplified by the amplifier in the PCM Codec (IC851) and the ALC
(IC852), then input as the built-in microphone to the PCM Codec (IC851) again.
When the level of the input sound signal is more than the specified value, the gain is changed and the output signal level is
kept constant at the ALC (IC852). Sound distortion is controlled when the input is excessive.
2. In the PCM Codec (IC851), after the sound signal is switched between the built-in microphone and the external microphone
by a register setting from the host, amplification, AD conversion and gain adjustment are performed.
The sampling frequency of the A/D conversion is 8kHz and it is converted to the PCM in the format of 8bit and µ law. Then,
64kbps data are output to the CPU (IC101) through the Serial I/F.
The data transfer of the Serial I/F is BCLK (256 kHz).
3. The data compression of 32kbps is performed in the ADPCM Block of the CPU (IC101) and the data transferred as sound
data.
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