Data Sheet

Bluegiga Technologies Oy
Page 27 of 44
9 PCM Codec Interface
PCM is a standard method used to digitize audio (particularly voice) for transmission over digital
communication channels. Through its PCM interface, WT41-E has hardware support for continual
transmission and reception of PCM data, thus reducing processor overhead for wireless headset applications.
WT41-E offers a bidirectional digital audio interface that routes directly into the baseband layer of the on-chip
firmware. It does not pass through the HCI protocol layer.
Hardware on WT41-E allows the data to be sent to and received from a SCO connection. Up to three SCO
connections can be supported by the PCM interface at any one time.
WT41-E can operate as the PCM interface master generating an output clock of 128, 256 or 512kHz. When
configured as PCM interface slave, it can operate with an input clock up to 2048kHz. WT41-E is compatible
with a variety of clock formats, including Long Frame Sync, Short Frame Sync and GCI timing environments.
It supports 13-bit or 16-bit linear, 8-bit µ-law or A-law companded sample formats at 8ksamples/s and can
receive and transmit on any selection of three of the first four slots following PCM_SYNC. The PCM
configuration options are enabled by setting PSKEY_PCM_CONFIG32.
WT41-E interfaces directly to PCM audio devices.
NOTE: Analog audio lines are very sensitive to RF disturbance. Use good layout practices to ensure noise
less audio. Make sure that the return path for the audio signals follows the forward current all the way as close
as possible and use fully differential signals when possible. Do not compromise audio routing.
9.1 PCM Interface Master/Slave
When configured as the master of the PCM interface, WT41-E generates PCM_CLK and PCM_SYNC.
Figure 16: PCM Interface Master
When configured as the Slave of the PCM interface, WT41-E accepts PCM_CLK rates up to 2048kHz.