Cirrus Logic CS48DV2B - Manual (Page 6)

CS48DV2B Data Sheet
32-bit Audio DSP for Dedicated Dolby Volume and Audistry by Dolby
6 Copyright 2009 Cirrus Logic DS875F2
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3. Code Overlays
The suite of software available for the CS48DV2B DSP consists of an operating system (OS) and a
library of overlays. The overlays have been divided into three main groups called Matrix-processors,
Virtualizer-processors, and Post-processors. All software components are defined below:
1. OS/Kernel - Encompasses all non-audio processing tasks, including loading data from external
memory, processing host messages, calling audio-processing subroutines, error concealment,
etc.
2. Matrix-processor- Any Module that performs a matrix decode on PCM data to produce more
output channels than input channels (2 Ö n channels). Examples are Dolby ® Pro Logic ® IIx and
DTS Neo:6 ™ . Generally speaking, these modules increase the number of valid channels in the
audio I/O buffer.
3. Virtualizer-processor - Any module that encodes PCM data into fewer output channels than
input channels (n Ö 2 channels) with the effect of providing “phantom” speakers to represent the
physical audio channels that were eliminated. Examples are Dolby Headphone
®
and Dolby ®
Virtual Speaker
®
. Generally speaking, these modules reduce the number of valid channels in the
audio I/O buffer.
4. Post-processors - Any module that processes audio I/O buffer PCM data in-place after the
matrix- or virtualizer-processors. Examples are the Dolby Volume and Audistry by Dolby
firmware, bass management, audio manager, tone control, EQ, delay, and customer-specific
effects
The bulk of each overlay is stored in ROM within the CS48DV2B, but a small image is required to
configure the overlays and boot the DSP. This small image can either be stored in an external serial
FLASH/EEPROM, or downloaded via a host controller through the
SPI ™ /I
2
C ® serial port.
The overlay structure reduces the time required to reconfigure the DSP when a processing change is
requested. Each overlay can be reloaded independently without disturbing the other overlays. For
example
, when a new matrix-processor is selected, the OS, virtualizer-, and post-processors do not
need to be reloaded — only the new matrix-processor. This fact is also true for the other overlays.
Table 2 lists the firmware available based on device selection. Please refer to AN298, CS485xx
Firmware User’s Manual for the latest listing of application codes and Cirrus Framework ™ modules
available.