CS485xx Family Data Sheet

32-bit Audio Decoder DSP Family

6

Copyright 2009 Cirrus Logic, Inc.

DS734F3

CONFIDENTIAL

3. Code Overlays

The suite of software available for the CS485xx family 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 n channels). Examples are Dolby ProLogic 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 2 channels) with the effect of providing “phantom” speakers to represent 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 bass management, audio manager, tone control,

EQ, delay, customer-specific effects, etc.

The bulk of each overlay is stored in ROM within the CS485xx, 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

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

need to be reloaded — only the new matrix-processor (the same is true for the other overlays).

Table 2 below lists the firmware available based on device selection. Please refer AN298, CS485xx

available.