User's Manual

LTE Module
EC20 Hardware Design
EC20_Hardware_Design Confidential / Released 40 / 83
3.12. PCM and I2C Interface
EC20 provides one Pulse Code Modulation (PCM) digital interface for audio design, which supports the
following modes:
 Primary mode (short sync, works as both master and slave)
 Auxiliary mode (long sync, 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_CLK supports 128, 256, 512,
1024, 2048 and 4096kHz for different speech codec.
In auxiliary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge; while the PCM_SYNC rising edge represents the MSB. In this mode, PCM interface operates with a
128kHz PCM_CLK and an 8kHz, 50% duty cycle PCM_SYNC only.
EC20 supports 8-bit A-law and μ-law, and also 16-bit linear data formats. The following figures show the
primary mode’s timing relationship with 8kHz PCM_SYNC and 2048kHz PCM_CLK and auxiliary mode’s
timing relationship with 8kHz PCM_SYNC and 128kHz PCM_CLK.
PCM_CLK
PCM_SYNC
PCM_OUT
MSB
LSB
MSB
MSB
LSB
MSB
PCM_IN
125us
1 2 256255
Figure 22: Primary Mode Timing