Syllabus Introduction to Embedded System Design HW/SW Codesign Overview Cospecification and modeling Embedded System partitioning CPU and Accelerator based Embedded System Codesign Embedded Computer Organization Embedded System controller case studies Embedded SoPC: Virtex System on Programmable Chips
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Hardware Software Codesign of Embedded Systems
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Siamak Mohammadi Tehran University
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Syllabus 9. 10. 11. 12.
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References
Compilers for Embedded Systems Real-time operating systems System level power/energy optimization HW/SW Codesign environments
Hardware/Software Co-Design: Principles and Practices
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J. Staunstrup and W. Wolf, Kluwer 1997
Embedded System Design: A Unified Hardware/Software Approach
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HW/SW Codesign of Embedded Systems Tehran University
Frank Vahid and Tony Givargis, 1999
Papers
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Course goals
Course goals (cont.)
Show benefits of the codesign approach over current design process Provide information on how to incorporate these techniques into a general digital design methodology for embedded systems
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Introduction
Software and hardware components of an embedded system
Understand real-time operating systems Embedded Computer Architecture
Illustrate how codesign concepts are being introduced into design methodologies Introduce the fundamentals of HW/SW codesign and partitioning concepts in designing embedded systems Discuss the current trends in the codesign of embedded systems Provide information on the goals of and methodology for partitioning hardware/software in systems
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What is an Embedded (real-time) System? Most embedded systems are also real-time systems. An embedded system is an information processing system that responds to externally generated input stimuli within a finite and specified period.
What are Embedded Systems? Difficulties with the design of heterogeneous HW/SW Systems Requirements of modern embedded systems Embedded Systems Design Flow Embedded Systems Application
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The correctness depends not only on the logical result but also the time it was delivered Failure to respond is as bad as the wrong response!
Embedded system: any device that includes a programmable computer but is not itself a generalpurpose computer Take advantage of application characteristics to optimize the design:
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HW/SW Codesign of Embedded Systems Tehran University
Don’t need all the general-purpose bells and whistles.
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Embedding a computer
Embedded Systems
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Real-time systems process events Events occurring on external inputs cause other events to occur as outputs Minimizing response time is usually a primary objective, or otherwise the entire system may fail to operate properly Types of Embedded Real Time System:
Hard real-time Soft real-time Firm real-time
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HW/SW Codesign of Embedded Systems Tehran University
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Types of Real-Time Systems
Embedded Real Time Systems
Electronic devices that incorporate a computer (microprocessor/micro-controller) in their implementation A computer is used in such devices primarily as a means to simplify the system design and to provide flexibility Often the user of the device is not even aware that a computer is present Embedded Systems are every where Embedded processors account for more than 90% of worldwide microprocessor production. Embedded:desktop = 100:1 99% of all processors are for the embedded systems market. Number of embedded processors in a typical home is estimated at 50-60 (a recent Acura automobile has more than 48 processors)
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Hard real-time — systems where it is absolutely imperative that the responses occur within the required deadline. For ex: Flight control systems, heart pace makers Soft real-time — systems where deadlines are important but which will still function correctly if deadlines are occasionally missed. For ex: dropping frames while displaying a video Firm real-time — allow occasional deadline violations but discard any jobs that are not finished by their deadlines
A single system may have all hard, soft and firm real-time subsystems. In reality many systems will have a cost function associated with missing each deadline.
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Multi-tasking and Concurrency
Embedded Systems Applications
Most embedded systems have several inputs/outputs and multiple events occurring independently Separating tasks simplifies programming, but requires somehow switching back and forth among multiple tasks (multitasking) Concurrency is the appearance of simultaneous execution of multiple tasks Concurrent task for a Thermostat: /* Monitor Temperature*/ do forever { measure temp ; if (temp < setting) start furnace ; else if (temp > setting + delta) stop furnace ; }
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/* Monitor Time of Day */ do forever { measure time ; if (6:00am) setting = 26C ; else if (11:00pm) setting = 20C ; }
Embedded Systems Applications
Dishwashers, microwave ovens, VCRs, televisions, stereos, fire/security alarm systems, lawn sprinkler controls, thermostats, cameras, clock radios, answering machines
Data collection, oscilloscopes, signal generators, signal analyzers, power supplies HW/SW Codesign of Embedded Systems Tehran University
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Imaging systems (e.g., XRAY, MRI, and ultrasound), patient monitors, and heart pacers FAX machines, copiers, telephones, and cash registers
Personal:
Elevator controls, surveillance systems, robots
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Office automation:
Instrumentation:
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Medical:
Industrial:
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Printers, scanners, keyboards, displays, modems, hard disk drives, CD-ROM drives
Home:
Satellites, network routers, switches, hubs
Embedded Systems Applications
Computer peripherals:
Nintendo's "Game Boy“ …
Communications:
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Fuel injection control, passenger environmental controls, anti-lock braking, air bag controls, GPS mapping
Children toys:
Navigation systems, automatic landing systems, flight attitude controls, engine controls, space exploration (e.g., the Mars Pathfinder)
Automotive:
/* Monitor Keypad */ do forever { check keypad ; if (raise temp) setting++ ; else if (lower temp) setting-- ; }
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Aerospace spacecrafts:
Personal Digital Assistants (PDAs), pagers, cell phones, wristwatches, video games, portable MP3 players, GPS
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Parts of an Embedded System
Parts
EMBEDDED SYSTEM
USER
I/O
HARDWIRED UNIT • Application-specific logic • Timers • A/D and D/A conversion
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ACTUATORS
PROCESSOR
SENSORS
MEMORY
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Microcontroller: includes I/O devices, on-board memory Digital signal processor (DSP): microprocessor optimized for digital signal processing. Typical embedded word sizes: 8-bit, 16-bit, and 32-bit.
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Today’s high-end automobile may have 100 microprocessors:
Control fuel/air mixture, engine timing, etc. Multiple modes of operation: warm-up, cruise, hill climbing, etc. Provides lower emissions, better fuel efficiency
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Automotive Embedded Systems
First microprocessor was Intel 4004 in early 1970’s HP-35 calculator used several chips to implement a microprocessor in 1972 Automobiles used microprocessor-based engine controllers starting in 1970’s
Range of implementation options Single-chip implementation: system on a chip
ENVIRONMENT
Early History of Embedded Systems
Actuators - mechanical components (e.g., valve) Sensors - input data (e.g., accelerometer for airbag control) Data conversion, storage, processing Decision-making
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4-bit microcontroller checks seat belt Microcontrollers run dashboard devices 16/32-bit microprocessor controls engine
BMW 850i brake and stability control system
Anti-lock brake system (ABS): Pumps brakes to reduce skidding. Automatic Stability Control (ASC+T): Controls engine to improve stability ABS and ASC+T communicate. ABS was introduced first--ASC+T needed to interface to existing ABS module.
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Anti-lock Brake System (ABS)
Embedded System Applications
Sensor
Sensor
Brake
Brake
Programmable Digital Thermostat
ABS
Hydraulic pump
Brake
Brake
Sensor
Sensor
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4-bit microprocessor
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Embedded System Applications
Embedded System Applications
NASA’s Mars Rover
Palm Vx Handheld
Intel 80C85 8-bit microprocessor
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32-bit CPU Motorola Dragonball EZ
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Embedded System Applications
Embedded System Applications
DVD Player
IBM Research’s Linux Wrist Watch Prototype
32-bit RISC Microprocessor
Hardware
Software
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CPU: High speed, low power 32 bit MPU (18-74 MHz) Input devices: Touch panel, button Display: 320 x 240 dots, monochrome liquid crystal display Memory: 8MB low power DRAM, 16MB flash Interfaces: Bluetooth wireless technology (v1.1, voice-enabled), IrDA (V1.2), RS232C (via a cradle) Others: Speaker, microphone, vibrator, fingerprint sensor, accelerator sensor Cradle: RS232C, AC adapter, and AA batteries Operating system: Linux kernel version 2.4 GUI: Microwindows Bluetooth stack: IBM BlueDrekar (L2CAP, SDP, RFCOMM)
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Embedded System Applications
Embedded System Applications
SONY Aibo Robot Dog
Vending Machine
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8-bit Motorola 68HC11 Microcontroller
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Embedded Real-time System Features
Characteristics of Embedded Systems
Large and complex — vary from a few hundred lines of assembler or C to 20 million lines of Ada Concurrent control of separate system components — devices operate in parallel in the real world; better to model this parallelism by concurrent entities in the program Facilities to interact with special purpose hardware — need to be able to program devices in a reliable and abstract way Extreme reliability and safe — embedded systems typically control the environment in which they operate; failure to control can result in loss of life, damage to environment or economic loss Guaranteed response times — we need to be able to predict with confidence the worst case response times for systems; efficiency is important but predictability is essential
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Embedded Systems Non-Functional Requirements
Performance Cost
Manufacturing cost Power
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Why Use Microprocessors?
Alternative to custom logic, FPGAs Efficient way to implement digital systems Can built various feature sets for different products using same logic Simplify the design of products μp-based designs can be as fast because:
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Several real-time activities at the same time for example audio and video multimedia
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Critical in battery-powered systems Excessive power consumption increases system cost even in wall-powered devices Custom logic is the clear winner for low power devices Software techniques can help reduce power consumption
Complex algorithms: filtering functions in cars User Interface: moving maps in GPS
Real Time operations Multirate
Manufacturing cost must often be low NRE (non-recurring engineering)
Sophisticated functionality
Physical size and weight Power consumption
μps execute programs very efficiently (RISC: one instruction per cycle) CPUs run at very high speed Heavily pipelined Aggressive VLSI technology
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Challenges in Embedded System Design
Run slower? Turn off unnecessary logic? Reduce memory access?
How do we consider upgradeability?
Faster HW or cleverer SW?
How do we minimize power?
How big is the CPU, Memory, Peripheral devices?
How do we meet deadlines?
Design Methodology: A procedure for designing a system
How much hardware do we need?
Challenges in Embedded System Design
Add features by changing SW for next product generation
Reliability
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Question: What are Design Goals?
Help automate methodology steps Keep track of the methodology itself
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StreetPilot GPS Receiver 16-bit
Performance
Understanding your methodology helps you ensure you didn’t skip anything Compilers, software engineering tools, computer-aided design (CAD) tools, etc., can be used to:
Finding bugs in safety-critical systems before selling it!
Requirements, Specification, Architecture, components, System Integration
microprocessor
Overall speed, deadlines.
Functionality and user interface Manufacturing cost Power consumption Other requirements (physical size, etc.)
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Requirements Analysis of a GPS Moving Map
GPS Moving Map Needs
Moving
Functionality:
User interface:
map obtains its position from the GPS (satellite-based navigation system) Paints map from the local database
User’s current position
Cost:
Physical size/weight:
Power consumption:
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Map should scroll smoothly. No more than 1 sec power-up. Lock onto GPS within 15 seconds
Lat: 20 12 long:40 15
At least 400 x 600 pixel screen. Three buttons max. Pop-up menu.
Performance:
Kurdistan
Hemat
For automotive use. Show major roads and landmarks.
$700 street price = approx. $150 cost of goods sold Should fit in hand Should run for 8 hours on four AA batteries
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GPS Moving Map Requirements form
Specification
Name
GPS moving map
Purpose
Consumer-grade moving map for driving
Inputs
Power button, three control buttons
Outputs
Back-lit LCD 400 X 600
Functions
5-receiver GPS; three resolutions; displays current latitude/longitude
Performance
Updates screen within 0.25 sec of movement
A more precise description of the system: Should not imply a particular architecture; Provides input to the architecture design process May include functional and non-functional elements May be executable or may be in mathematical form for proofs It Should include:
Manufacturing cost
$100 cost-of-goods-sold
Power
100 mW
Physical size/weight
No more than 2 X 6, 12 oz
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What is received from GPS; map data; user interface; operations required to satisfy user requests; background operations needed to keep the system running.
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System Architecture Design
Moving Map Block Diagram
What major components needed to satisfy the specification? Hardware components:
Software components:
CPUs Memory, Peripherals, etc. Major programs and their operations
Must take into account functional and nonfunctional specifications
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GPS HW Architecture
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GPS SW Architecture
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An embedded system example: a digital camera
Hardware Software Components
Must spend time architecting the system before you start coding Some components are ready-made, some can be modified from existing designs, and others must be designed from scratch System Integration
CCD preprocessor
JPEG codec
Memory controller
Have a plan for integrating components to uncover bugs quickly, test as much functionality as early as possible HW/SW Codesign of Embedded Systems Tehran University
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Display ctrl
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Many systems have complex embedded hardware and software
UART
LCD ctrl
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Design methodology help us manage the design process HW/SW Codesign of Embedded Systems Tehran University
HW/SW Codesign Overview Modeling and co-specification of Embedded Systems
Design time Power Performance Deadlines
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ISA bus interface
What comes next?
Embedded systems pose many design challenges:
Multiplier/Accum
Single-functioned -- always a digital camera Tightly-constrained -- Low cost, low power, small, fast Reactive and real-time -- only to a small extent
Embedded Systems are all around us
Microcontroller
DMA controller
Summary
D2A
lens
Many bugs appear only at this stage
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Pixel coprocessor
A2D
Put together the components
Digital camera chip CCD
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SystemC as a specification language
Partitioning and Scheduling Hardware Accelerator based Embedded Systems Embedded Computer Organization Code generation and retargetable Compilers Real-time operating systems System Level Power/Energy Optimization Etc.
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