Cirrus-logic CS48DV2B User Manual download pdf (Page 6)

CS48DV2B Data Sheet

32-bit Audio DSP for Dedicated Dolby Volume and Audistry by Dolby

CONFIDENTIAL

CONFIDENTI

DRA

ELPHI

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 (2Ön 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 (nÖ2 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

™

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.

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