BC352239A Datasheet, PDF (73/116 Pages) List of Unclassifed Manufacturers – BlueCore 3-Multimedia External

Device Terminal Descriptions
8.8.1 Stereo CODEC Setup
The configuration and control of the ADC is through VM functions which are described in appropriate BlueLab
Multimedia documentation. This section covers an overview of the parameters that can be set up using the VM
functions.
The Kalimba DSP can communicate its requirements of the CODEC to the MCU and hence the VM by exchange
of messages. The messages used between the Kalimba DSP and the embedded MCU are based on interrupts:
one interrupt between the MCU and Kalimba DSP and one interrupt between the Kalimba DSP and the MCU.
Message content is transmitted using shared memory. There are VM and DSP library functions to send and
receive messages; for further details refer to BlueLab Multimedia documentation.
8.8.2 ADC
The ADC consists of two second order Sigma Delta converters allowing two separate channels that are identical
in functionality, as shown in Figure 8..
8.8.3 ADC Sample Rate Selection and Warping
Each ADC supports the following sample rates:
! 8kHz
! 11.025kHz
! 16kHz
! 22.05kHz
! 24kHz
! 32kHz
! 44.1kHz
One of the main concerns for stereo wireless music applications is the ability to keep sample rates for the
CODECs at both ends of the wireless link in synchronisation. A VM function adjusts the sample rate using a
‘warping’ function to tune the sample rate to the required value. The ADC warp function allows the sample rate to
be changed by ±3%, in steps of 1/2¹⁷, or 7.6 ppm. The warp function preserves the signal quality – the distortion
introduced when warping the sample rate is negligible.
8.8.4 ADC Gain
The ADC contains two gain stages for each channel, an analogue and a digital gain stage.
The digital gain stage has a programmable selection value in the range of 0 to 15 with the associated ADC gain
settings summarised in Table 8.20.
BC352239A-ds-001Pc
© Cambridge Silicon Radio Limited 2004
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