Embedded Software in Real-Time Signal Processing Systems: Application and Architecture Trends
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Transcript of 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
Presented by Cedric Ma
for EE249
09/04/2001
Gert Goossens, Johan Van Praet, Dirk Lanneer, Werner Geurts, Augusli Kifli Clifford Liem, and Pierre G. PaulinProceedings of the IEEE, Vol 85, No. 3, March 1997
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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– AT&T: 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
“Today’s General-Purpose Processors Solve Yesterday’s 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– MCU:low code size; DSP:execution 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 processor’s 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