Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 49 / 82
3.9. PCM Interface
M66 supports PCM interface. It is used for digital audio transmission between the module and the 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 12: Pin Definition of PCM Interface
3.9.1. Configuration
M66 module supports 16-bit 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 interface supports both long and short
synchronization simultaneously. Furthermore, it only supports MSB first. For detailed information, please
refer to the table below.
Ref level 0 4.8 Vpp
AOUT2
Output
Single-ended
Load resistance 32
Load
Resistance
Reference level 0 2.4 Vpp
Pin Name Pin No. Description
PCM_CLK 30 PCM clock output
PCM_SYNC 31 PCM frame synchronization output
PCM_IN 32 PCM data input
PCM_OUT 33 PCM data output