Cirrus Logic CS4970x4 - Manual (Page 94)

Introduction
CS4953x4/CS4970x4 System Designer’s Guide
DS810UM6 Copyright 2013 Cirrus Logic, Inc 7-1
Chapter 7
Overview of Common Firmware Modules
7.1 Introduction
The purpose of this chapter is to serve as an introduction to firmware operation on the CS4953x4/
CS4970x4 DSP This chapter explains the general framework of operation on the CS4953x4/CS4970x4.
• New boot code now boots off the customer’s SPI Flash device and allows the CS4953x4/CS4970x4
DSP chips to manage all boot tasks. See
Chapter 1, "Operational Modes" for information about the
boot process for the CS4953x4/CS4970x4 DSP chips.
• CS4953x4/CS4970x4 DSP chips carry out duties previously performed by the system’s
microcontroller:
- DSP auto-switches overlays
- DSP detects sample rate
Note: Systems using the Cirrus CS4953x4/CS4970x4 DSP chips are based on the assumption that
dedicated Flash memory is available to the DSP. DSP processing activities such as auto-
switching are more affected by the speed and memory size of the customer’s Flash device
than by the capability of the system microcontroller, and should be faster than previous system
designs.
7.2 CS4953x4/CS4970x4 Firmware
7.2.1 Firmware Modules
The CS4953x4/CS4970x4 DSP provides both standard and advanced audio decoding and processing
using factory-supplied firmware modules that are downloaded to the device and executed on one of the
DSP cores. Each module provides a specific processing functionality. For instance, the DTS module
provides DTS ® decoding, the Dolby Headphone ® module provides Dolby Headphone processing
capability and the Bass Management module provides Bass Management processing.
7.2.2 Overlay Architecture
For memory management reasons, modules are grouped into overlays, which are separately loadable.
Most overlays have a one-to-one correspondence with modules. Post processing overlays (PPMs)
generally have a one-to-many correspondence: one overlay contains many modules.
Overlays are divided into classes, based on the type of audio processing the modules in that overlay class
do. In the CS49700, the following overlay classes are defined:
• OS - operating system functions
• DEC - decoder modules (for example, AC3, DTDHDHRA)
• MPM - matrix processing modules (for example, PL2, NEO6, COMS2)
• VPM - virtualizer modules (for example, Dolby Headphone)
• PPM - post processor modules
At any given moment, only one overlay of each class can be loaded in the DSP (the OS actually is loaded
into both DSP cores, DSP A and DSP B).