Embedded Software in Real-Time Signal Processing Systems: Application and Architecture Trends

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Embedded Software in Real-Time Signal Processing
Systems Application and Architecture Trends
Gert Goossens, Johan Van Praet, Dirk Lanneer,
Werner Geurts, Augusli Kifli Clifford Liem, and
Pierre G. Paulin Proceedings of the IEEE, Vol 85,
No. 3, March 1997

• Presented by Cedric Ma
• for EE249
• 09/04/2001

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Outline

• I. Introduction
• II. Market Processor Trends
• III. Embedded Processors in Multimedia, Wireless,
  Telecom
• IV. Embedded Systems Application Trends
• V. Embedded Software Development Needs

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Some Terms

• ASIP - application specific instruction-set
  processor cores
• MPU - Microprocessor Unit
• MCU - Microcontroller Unit
• DSP - Digital Signal Processor

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I. Introduction

• Telecom, Multimedia, Consumer Electronics
• Rapid evolution toward single chip integration
• Range of solutions general purpose cores to ASIP
• Future role of embedded processors?
• Convergence of computing, communication, and
  consumer electronics short time-to-market, very
  low costs
• Stabilization of PC market growth
• Increasing growth of wireless and multimedia
• Consumer oriented applications most influential
  to technology evolution in early 21st century
• especially wireless communications, multimedia

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II. Market Processor Trends

• A. Overall Semiconductor
• B. Embedded Processor

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A. Overall Semiconductor

• Two key trends
• Continued growth of Processors Memories
• Growth leaders are Multimedia Wireless
• New Technology Drivers
• General purpose computing chips and memories in
  the past were main contributor to evolution of
  VLSI technology and design methods
• New role assumed by
• Wireless GSM, DECT cordless phone
• Multimedia MPEG2 decoders, DVD, HDTV

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B. Embedded Processor Trends

• Main application classes for programmable
  processors
• Computing Applications
• Desktop, notebooks, workstations, server
• characterized by user programmability
• Embedded Applications
• More specific
• Dedicated function ABS, autopilot
• Real-time behavior (strict requirements)
• Correctness of design (impact to environment)

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B Embedded Processor Classes

• Embedded Processors
• Instruction-set programmable processors used in
  embedded systems
• Include MCU, DSP, MPU (CISC RISC)
• ASIP
• Programmable processor for specific, well-defined
  class of applications
• Small, well-defined instruction set
• Specialized/stripped down versions of MCU/DSP/MPU
• Applications real-time signal/image processing

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B Processor Volume Distributions

• Parts volume dominated by 4 8-bit MCU
• MPU 60 total processor sales revenue
• but lower volume than MCU DSP
• reason higher price of MPU
• 32-bit Processors
• Uses 43 computing / 57 embedded
• x86-based
• 90 (revenue) of computing applications market
• 30 of embedded market diversity of architectures

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III. Embedded Processors in Multimedia, Wireless,
Telecom

• Multimedia
• set-top boxes, HDTV, DVB, videophones
• Wireless communication
• GSM, DECT, IS-54B digital cellular
• Telecommunications
• broad range of high volume products

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A1. Multimedia Processors

• Widespread use of custom ASIP cores
• Low cost
• Most revenue comes from 2nd generation
  cost-reduced versions
• 32-bit MPU not well suited
• Specialized video compression algorithms
• No need for processor cache
• Software compatibility not an issue
• Carefully optimized set of specific tasks

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A2. 3-D Video Acceleration

• Most vendors use dedicated ASIP
• Lack of standard RISC/CISC MPU
• Reason high performance requires dedicated
  architectures
• MMX for x86 (introduced 1997)
• Allows 3-D processing in software
• 10x speedup needed to handle high-quality game
  programs

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B. Wireless Communications

• ASIP the preferred choice
• France Telecom ASIP achieved 50 power reduction
  over commercial DSP
• Italtel 2 in-house ASIP replaced 8 commercial
  DSP in GSM base station
• ATT ASIP design is a key advantage
• Northern Telecom ASIP used in many strategic
  high-volume products

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C. General Telecom

• Northern Telecom survey
• Number of design teams using
• 2/3 of teams use commercial DSP/MCU chips
• Number of processors shipped
• 2/3 in-house ASIP, 1/3 commercial
• What this means
• ASIP large volume, low cost applications
• Commercial minimize time-to-market

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D. Embedded Processor Conclusions

• Diversity of processor architectures
• Driven by low-cost consumer markets
• Diversity of building blocks
• RISC/ASIP/hard-wired co-processors
• Dominance of ASIP
• High-volume, low cost segments

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D ASIP vs. General Purpose Processors

• Todays General-Purpose Processors Solve
  Yesterdays Problems
• Applications themselves do not stand still
• Dedicated multimedia processor more cost
  effective
• API for x86 can be mapped to low cost ASIP

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D Outlook for Embedded Systems Market

• Emerging (consumer) embedded applications
  expected to be available at competitive prices
• Justify development of dedicated ASIP
• General purpose processors continue to dominate
  low volume applications
• Not clear cut ASIP often coupled with RISC or MCU

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IV. Embedded Systems Application Trends

• Growth of Complexity
• New wireless handsets features, cell phone/PDA
  merge, videophone standard, new video audio
  coding standards
• Many functions moved from hardware to software
• ASIP required for performance cost reasons

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V. Embedded S/W Development Needs

• Design teams developing embedded software require
  sophisticated tools
• Commercial tool support trends
• Northern Telecom survey
• Ideal hardware-software codesign tool environment

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A. Processor Tool Support Trends

• Commercial C compilers low quality
• MCUlow code size DSPexecution speed
• 4-10x slower than hand coded assembly
• Embedded design no speed degradation!
• Designers continue to program in assembly code
• Long term problem assembly code locks designers
  to old architectures

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B. Northern Telecom Survey

• Dominance of assembly
• ANSI C is the only high-level language used
• Assembly preferred for algorithm capture
• MCU 75 of code DSP 90
• Poor quality of generated assembly code
• Unwilling to sacrifice performance
• DSP code has greater portion written in assembly

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B. Northern Telecom Survey

• Development effort rapidly increasing
• embedded software development effort exceeds
  hardware-oriented development
• Future tool needs
• Improved compiler technology
• allows high-level language for expressing
  algorithm
• High-performance instruction-set simulator
• Source-level debugger
• Cross assembler remap legacy code

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C. Embedded S/W Needs

• High-performance compilers for low-cost irregular
  architectures
• Environment that supports rapid development of
  compilers
• Associated tools performance profilers,
  source-level debuggers, in-circuit emulators
  retargetable
• ASIP based designs quick feedback on instruction
  set decisions
• Rapid deployment of cycle-accurate instruction
  set models
• Synthesis of lightweight RTOS

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C Ideal hardware-software co-design environment

• Key characteristic of ideal environment
• Functional co-simulation allows validation of
  global behavior of software and hardware
• Retargetable compiler (to new platforms)
• source-level debugging complete
  assembler/linker back-end
• Instruction set definition used to generate model
  of target processors instruction set
• permits execution of object code on virtual model
  of processor
• Allows for exploring ASIP architectures
• Profile tool measures performance guides
  instruction set selection