Laird BT830, Hardware Integration Manual

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BT830 Hardware Integration Guide
Version 0.1 (PRELIMINARY)
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20 CONN-GUIDE-BT830
(PRELIMINARY)
8.10 PCM_CLK and PCM_SYNC Generation
BT830 has two methods of generating PCM_CLK and PCM_SYNC in master mode:

Generating these signals by DDS from BT830internal 4MHz clock. Using this mode limits PCM_CLK to 128, 256
or 512 kHz and PCM_SYNC to 8 kHz.

Generating these signals by DDS from an internal 48MHz clock, which enables a greater range of frequencies
to be generated with low jitter but consumes more power. To select this second method set bit
48M_PCM_CLK_GEN_EN in PSKEY_PCM_CONFIG32. When in this mode and with long frame sync, the length
of PCM_SYNC is either 8 or 16 cycles of PCM_CLK, determined by LONG_LENGTH_SYNC_EN in
PSKEY_PCM_CONFIG32.
Equation 8.1 describes PCM_CLK frequency when generated from the internal 48MHz clock:
Equation 8.1: PCM_CLK Frequency Generated Using the Internal 48MHz Clock
Set the frequency of PCM_SYNC relative to PCM_CLK using Equation 8.2:
Equation 8.2: 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 SKEY_PCM_LOW_JITTER_CONFIG to 0x08080177.
8.11 PCM Configuration
Configure the PCM by using PSKEY_PCM_CONFIG32 and PSKEY_PCM_LOW_JITTER_CONFIG (See your PSKey file).
The default for PSKEY_PCM_CONFIG32 is 0x00800000 (for example: 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-state of PCM_OUT).
8.12 Digital Audio Interface (I²S)
The digital audio interface supports the industry standard formats for I²S, left-justified or right-justified. The interface
shares the same pins as the PCM interface, which means each audio bus is mutually exclusive in its usage.
Table 12
lists these alternative functions. Figure 11 shows the timing diagram.
Table 12: Alternative Functions of the Digital Audio Bus Interface on the PCM Interface.
PCM Interface I²S Interface
PCM_OUT SD_OUT
PCM_IN SD_IN
PCM_SYNC WS
PCM_CLK SCK