Specifications

PCM_OUT

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Audio gain

13-bit sample

Figure 34: 16-bit slot with 13-bit linear sample and audio gain selected

7.4.7 Additional Features

WT32 has a mute facility that forces PCM_OUT to be 0. In Master mode, PCM_SYNC may

also be forced to 0 while keeping PCM_CLK running, which some CODECS use to control

power down.

7.4.8 PCM CLK and SYNC Generation

WT32 has two methods of generating PCM_CLK and PCM_SYNC in master mode. The first

is generating these signals by Direct Digital Synthesis (DDS) from BlueCore5 Multimedia

External internal 4MHz clock. Using this mode limits PCM_CLK to 128, 256 or 512kHz and

PCM_SYNC to 8kHz. The second is generating PCM_CLK and PCM_SYNC by DDS from an

internal 48MHz clock (which allows a greater range of frequencies to be generated with

low jitter, but consumes more power). The second method is selected by setting bit

48M_PCM_CLK_GEN_EN in PSKEY_PCM_CONFIG32. When in this mode and with long

frame sync, the length of PCM_SYNC can be either 8 or 16 cycles of PCM_CLK, determined

by LONG_LENGTH_SYNC_EN in PSKEY_PCM_CONFIG32.

Equation 3 describes PCM_CLK frequency when being generated using the internal 48MHz

clock:

Equation 3: PCM_CLK frequency when being generated using the internal 48 MHz clock

The frequency of PCM_SYNC relative to PCM_CLK can be set using Equation 4

Equation 4: PCM_SYNC frequency relative to PCM_CLK

CNT_RATE, CNT_LIMIT and SYNC_LIMIT are set using PSKEY_PCM_LOW_JITTER_CONFIG.

As an example, to generate PCM_CLK at 512kHz with PCM_SYNC at 8kHz, set

PSKEY_PCM_LOW_JITTER_CONFIG to 0x08080177.

7.4.9 PCM Configuration

The PCM configuration is set by using two PS Keys, PSKEY_PCM_CONFIG32 and

PSKEY_PCM_LOW_JITTER_CONFIG. The following tables detail these PS Keys. The default

for PSKEY_PCM_CONFIG32 key is 0x00800000, i.e. first slot following sync is active, 13-bit

linear voice format, long frame sync and interface master generating 256kHz PCM_CLK

from 4MHz internal clock with no tri-stating of PCM_OUT.

PSKEY_PCM_LOW_JITTER_CONFIG is described in Table 23.