Pcm And I2C Interfaces - Quectel LTE-A Series Hardware Design

3.12. PCM and I2C Interfaces

EG18 supports audio communication via Pulse Code Modulation (PCM) digital interface and I2C
interfaces.
The PCM interface supports the following modes:

Primary mode (short frame synchronization, works as both master and slave)

Auxiliary mode (long frame synchronization, works as master only)
In primary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge. The PCM_SYNC falling edge represents the MSB. In this mode, PCM interface supports 256kHz,
512kHz, 1024kHz or 2048kHz PCM_CLK at 8kHz PCM_SYNC, and also supports 4096kHz PCM_CLK at
16kHz PCM_SYNC.
In auxiliary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge. The PCM_SYNC rising edge represents the MSB. In this mode, PCM interface operates with a
256kHz PCM_CLK and an 8kHz, 50% duty cycle PCM_SYNC only.
EG18 supports 16-bit linear data format. The following figures show the primary mode's timing
relationship with 8kHz PCM_SYNC and 2048kHz PCM_CLK, as well as the auxiliary mode's timing
relationship with 8kHz PCM_SYNC and 256kHz PCM_CLK.
PCM_CLK
PCM_SYNC
PCM_OUT
PCM_IN
EG18_Hardware_Design
125us
1 2
MSB
MSB
Figure 27: Primary Mode Timing
LTE-A Module Series
EG18 Hardware Design
255 256
MSB
LSB
MSB
LSB
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