BC41B143A-ds-003Pc CSR, BC41B143A-ds-003Pc Datasheet - Page 75

• Manufacturer Part Number: BC41B143A-ds-003Pc
• Description: Blue Core ROM Plug-n-Go
• Manufacturer: CSR

PCM_CLK and PCM_SYNC Generation
BlueCore4-ROM Plug-n-Go 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 BlueCore4-ROM Plug-n-Go internal 4MHz clock
(which is used in BlueCore2-External). 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). This 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.
The Equation 10.8 describes PCM_CLK frequency when being generated using the internal 48MHz clock:
The frequency of PCM_SYNC relative to PCM_CLK can be set using Equation 10.9:
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.
BC41B143A-ds-003Pc
Equation 10.8: PCM_CLK Frequency When Being Generated Using the Internal 48MHz Clock
Equation 10.9: PCM_SYNC Frequency Relative to PCM_CLK
© Cambridge Silicon Radio Limited 2005
f
=
Advance Information
f
CNT
CNT
=
SYNC
PCM
_
_
RATE
LIMIT
_
_
LIMIT
CLK
×
24
×
MHz
8
Device Terminal Descriptions
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