6

DS734F5

3 Code Overlays

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 physical audio channels that were

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 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 FLASH/EEPROM, or downloaded via a host

The overlay structure reduces the time required to reconfigure the DSP when a processing change is requested. Each

is selected, the OS, virtualizer-, and post-processors do not need to be reloaded — only the new matrix-processor (the

same is true for the other overlays).

Table 3-1 lists the firmware available based on device selection. Refer AN298, CS485xx Firmware User’s

Table 3-1. Device and Firmware Selection Guide

Device

Suggested Application

Channel Count Input/Output

Package

CS48520-CQZ Digital TV, portable audio docking station, portable DVD, DVD mini/

receiver, multimedia PC speakers

Up to 4-channel in/4-channel out

48-pin QFP

CS48540-CQZ

CS48540-DQZ

CS48520 features plus 8-channel car audio, DVD receiver

Up to 8-channel in/8-channel out

48-pin QFP

CS48560-CQZ

CS48560-DQZ

CS48540 features plus 12-channel car audio, high-end digital TV, dual

source/dual zone SACD

Up to 12-channel in/12-channel out

48-pin QFP