1. Embedded System Design 王佑中 Yu-Chung Wang(ywang@redsonic.com)

2. What's in this course? ● Introduction to the embedded system. ● Introduction to the ARM9 architecture. ● Introduction to the ARM emulator(softgun) ● Bootloader ● The embedded Linux kernel. ● The embedded toolchain.

3. Reference ● Embedded Linux-Hardware, Software and interfacing: Craig Hollabaugh ● Linkers and Loaders: John R.Levine ● Linux Devices: http://www.linuxdevices.comhttp://www.linuxdevices.com ● Uclibc website http://www.uclibc.orghttp://www.uclibc.org ● Uclinux website http://www.uclinux.org

4. What's the requirements in this course? ● One midterm ● Execises ● One report

5. Introduction to embedded system

6. What are the embedded systems? ● Computers purchased as part of some other piece of equipment? – Vehicle – Air condition – MRT, airplane, robot ● It's difficult to cover embedded system by one sentence.

7. RFID card

8. Server appliance ● Multiple CPU ● Multi-GB RAM ● Disk Array ● Gigabit network ● …..

10. What's Different ? ● Embedded systems have different design constraints than general purpose computers – Cost may matter more than speed – Long life cycle may dominate design decisions – Reliability/safety may constrain design choices – Applying general purpose digital CAD tools isn't sufficient – System-level view must go beyond (digital) electronics – Must optimize across a broad span of product life cycle – Must deal with cross-functional & dysfunctional design cultures – Must deal with unique domain requirements – Business model varies by domain, and profoundly affects design decisions

11. Cost is very sensitive! ● Software solution – Optimize the code. – Cut down unnecessary functions. – A better and specialized system design. ● Hardware solution – SOC(Systenm on a chip) – Put more seperate components on a single chip. – Software/hardware co-design.

12. Long live cycle ● 10 years is not for long time for embedded system. ● For hardware vendor, they will use different strategy compared to the PC market. ● Intel – Petium is still in production. ● IBM, Motorolla – low solutions like 823,850,860, 403 is still in production.

13. Reliability/Safety ● Reactive ● Real-time ● Error Recovery

14. System level view ● Go beyond the computer – End-user's needs. – Domain knowledge – Business view – production view ● These are the key for competition – How to promote yourself

15. Challenge-Optimize your Design – Unit cost: the monetary cost of manufacturing each copy of the system, excluding NRE cost – NRE cost (Non-Recurring Engineering cost): The one-time monetary cost of designing the system – Size: the physical space required by the system – Performance: the execution time or throughput of the system – Power: the amount of power consumed by the system – Flexibility: the ability to change the functionality of the system without incurring heavy NRE cost – Time-to-prototype: the time needed to build a working version of the system – Time-to-market: the time required to develop a system to the point that it can be released and sold to customers – Maintainability: the ability to modify the system after its initial release – Correctness, safety, many more

16. UNIT and NRE COST ● Costs: – Unit cost: the monetary cost of manufacturing each copy of the system, excluding NRE cost – NRE cost (Non-Recurring Engineering cost): The one-time monetary cost of designing the system – total cost = NRE cost + unit cost * # of units – per-product cost = total cost / # of units = (NRE cost / # of units) + unit cost Example NRE=$2000, unit=$100 For 10 units total cost = $2000 + 10*$100 = $3000 per-product cost = $2000/10 + $100 = $300

17. Performance and flexibility ● Widely-used measure of system, widely-abused – Clock frequency, instructions per second – not good measures – Digital camera example – a user cares about how fast it processes images, not clock speed or instructions per second ● Latency (response time) – Time between task start and end – e.g., Camera’s A and B process images in 0.25 seconds ● Throughput – Tasks per second, e.g. Camera A processes 4 images per second – Throughput can be more than latency seems to imply due to concurrency, e.g. Camera B may process 8 images per second (by capturing a new image while previous image is being stored). ● Speedup of B over S = B’s performance / A’s performance – Throughput speedup = 8/4 = 2

18. Time to Market ● The most important factor in business ● Market window – Period during which the product would have highest sales ● Average time-to-market constraint is about 8 months ● Delays can be costly Revenues ($) Time (months)

19. The key of embedded system design ● Technology – A manner of accomplishing a task, especially using technical processes, methods, or knowledge ● Three key technologies for embedded systems – Processor technology – IC technology – Design technology

20. Processor technology ● General purpose processor – low time-to market cost – High flexibility ● Single purpose processor – fast, low-power, small ● Application purpose processor – Balance between flexibility and functionality – System On a Chip

21. IC technology ● Full-custom/VLSI ● Semi-custom ASIC (gate array and standard cell) ● PLD (Programmable Logic Device) – FPGA – CPLD

22. VLSI ● All layers are optimized for an embedded system’s particular digital implementation – Placing transistors – Sizing transistors – Routing wires ● Benefits – Excellent performance, small size, low power ● Drawbacks – High NRE cost (e.g., $300k), long time-to-market

23. semi-custom ● Lower layers are fully or partially built – Designers are left with routing of wires and maybe placing some blocks ● Benefits – Good performance, good size, less NRE cost than a full-custom implementation (perhaps $10k to $100k) ● Drawbacks – Still require weeks to months to develop

24. PLD ● All layers already exist – Designers can purchase an IC – Connections on the IC are either created or destroyed to implement desired functionality – Field-Programmable Gate Array (FPGA) very popular ● Benefits – Low NRE costs, almost instant IC availability ● Drawbacks – Bigger, expensive (perhaps $30 per unit), power hungry, slower