M50 Hardware Design
M50_HD_V2.0
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3.13. PCM interface
M50 supports PCM interface. It is used for digital audio transmission between the module and the
customer’s device. This interface is composed of PCM_CLK, PCM_SYNC, PCM_IN and
PCM_OUT signal lines.
Pulse-code modulation (PCM) is a converter that changes the consecutive analog audio signal to
discrete digital signal. The whole procedure of Pulse-code modulation contains sampling,
quantizing and encoding.
Table
21
:
Pin definition of PCM interface
Name
Pin
I/O
Description
PCM_CLK
19
O
PCM clock
PCM_IN
18
I
PCM data input
PCM_OUT
20
O
PCM data output
PCM_SYNC
21
O
PCM frame synchronization
3.13.1. Configuration
M50 supports 16 bits line code PCM format. The sample rate is 8 KHz, the clock source is 256
KHz, and the module can only act as master mode. The PCM interfaces support long and short
synchronization simultaneously. It only supports MSB first. For more detailed information, please
see the table below.
Table 22:
Configuration
PCM
Line interface format
Linear
Data length
Linear: 16 bits
Sampling rate
8KHz
PCM clock/synchronization
source
PCM master mode: clock and synchronization is generated
by module
PCM synchronization rate
8KHz
PCM clock rate
PCM master mode:256 KHz
PCM synchronization format
Long/short synchronization
PCM data ordering
MSB first
Zero padding
Yes
Sign extension
Yes
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