Figure 28: Primary Mode Timing - Quectel UC20 Manual

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.
UC20 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
PCM_IN
UC20_Hardware_Design
125us
1 2
MSB
MSB

Figure 28: Primary Mode Timing

Confidential / Released
UMTS/HSPA Module Series
UC20 Hardware Design
255 256
MSB
LSB
LSB
MSB
48 / 84