Panasonic BB-HCM381A Service Manual page 85

Sound Signal Flow
[Microphone sound]
1. The sound data input from A/V jack (CN504) is amplified by the
amplifier in the PCM CODEC (IC501) and the ALC (IC502), then input as
the built-in microphone to the PCM CODEC (IC501) again.
When the level of the input sound signal is more than the set value, the
gain is changed and the output signal level is kept constant at the ALC
(IC502). Sound distortion is controlled when the input is excessive.
2. In the PCM CODEC (IC501), by a register setting from the host,
amplification, A/D 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 É law. Then, 64kbps
data are output to the ASIC (IC103) through the Serial I/F.
The data transfer CLK of the Serial I/F is BCLK (256 kHz).
3. performed in the ADPCM Block of the ASIC (IC103) and the data is
transferred as sound data.
[Speaker Sound]
1. The ADPCM sound data are sent from the PC and decompressed in the
ADPCM block of the ASIC (IC103). The data are transferred as the
sound data of 64kbps to the PCM CODEC (IC501) through the Serial I/F.
2. After the law to linear conversion, amplification and D/A conversion
are performed, they are output to A/V jack (CN504) as sound output
signal in the PCM CODEC (IC501).
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