BT800 Hardware Integration Guide
Version 0.2
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CONN-GUIDE-BT800_v0_2
PCM_CLK and PCM_SYNC Generation
9.10
BT800 has 2 methods of generating PCM_CLK and PCM_SYNC in master mode:
Generating these signals by DDS from BT800internal 4MHz clock. Using this mode limits PCM_CLK to
128, 256 or 512kHz and PCM_SYNC to 8kHz.
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 9.1
describes PCM_CLK frequency when generated from the internal 48MHz clock:
Equation 9.1: PCM_CLK Frequency Generated Using the Internal 48MHz Clock
Set the frequency of PCM_SYNC relative to PCM_CLK using Equation 9.2:
Equation 9.2: 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.
PCM Configuration
9.11
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, 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-state of PCM_OUT.
Digital Audio Interface (I²S)
9.12
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 11
lists these alternative functions. Fig.13 shows the timing diagram.
Table 11: Alternative Functions of the Digital Audio Bus Interface on the PCM Interface.
PCM Interface
I
²
S Interface
PCM_OUT
SD_OUT
PCM_IN
SD_IN
PCM_SYNC
WS
