Panasonic KX-HCM110A Service Manual page 54

Amplifier for Auto Level Control
PCM Codec (IC601)
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 built-in microphone connector
(CN607) is amplified by the amplifier in the PCM Codec (IC601) and the
ALC (IC603), then input as the built-in microphone to the PCM Codec
(IC601) 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 (IC603). Sound distortion is controlled when the input is
excessive.
2. When the external microphone is attached to the microphone jack
(CN603), the sound signal input from pin 2 of the CN603 is amplified by
the amplifier in the PCM Codec (IC601) and the ALC (IC602), then input
as the external (microphone) to the PCM Codec (IC601) again
The ALC (IC602) works in the same way as the IC603.
3. In the PCM Codec (IC601), 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 law. Then, 64kbps
data are output to the ASIC (101) through the Serial I/F.
The data transfer of the Serial I/F is BCLK (256 kHz).
4. The data compression of 32kbps is performed in the ADPCM Block of
the ASIC (101) and the data transferred as sound data.
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