User's Manual

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7.4 PCM Interface
Pulse Code Modulation (PCM) is a standard method used to digitize audio (particularly voice) patterns
for transmission over digital communication channels. Through its PCM interface, WT32 has hardware
support for continual transmission and reception of PCM data, thus reducing processor overhead for
wireless headset applications. WT32 offers a bi directional 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 WT32 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 a time.
WT32 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. WT32 is
compatible with a variety of clock formats, including Long Frame Sync, Short Frame Sync and GCI
timing environments.
WT32 supports 13 or 16-bit linear, 8-bit -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 the PS Key PS KEY_PCM_CONFIG32 (0x1b3). WT32
interfaces directly to PCM audio devices including the following:
 Qualcomm MSM 3000 series and MSM 5000 series CDMA baseband devices
 OKI MSM7705 four channel A-law and -law CODEC
 Motorola MC145481 8-bit A-law and -law CODEC
 Motorola MC145483 13-bit linear CODEC
 STW 5093 and 5094 14-bit linear CODECs
 WT32 is also compatible with the Motorola SSI™ interface
7.4.1 PCM Interface Master/Slave
When configured as the Master of the PCM interface, WT32 generates PCM_CLK and PCM_SYNC.
PCM_OUT
PCM_IN
PCM_CLK
PCM_SYNC
8kHz
128/256/512 kHz
WT12
WTxx
Figure 24: WT32 as PCM master
When configured as the Slave of the PCM interface, WT32 accepts PCM_CLK and PCM_SYNC.
PCM_CLK rates up to 2048kHz are accepted.