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LTE-A Module Series
EG18 Hardware Design
EG18_Hardware_Design 55 / 104
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
MSB
LSB
MSB
125us
1
2
256
255
PCM_IN
MSB
LSB
MSB
Figure 27: Primary Mode Timing