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

1. 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 Embedded Software in Real-Time Signal Processing Systems: Application and Architecture Trends Presented by Cedric Ma for EE249 09/04/2001

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

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

4. 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

5. II. Market & Processor Trends • A. Overall Semiconductor • B. Embedded Processor

6. 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

7. 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)

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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