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1 - 1 Swiss Federal Institute of Technology Computer Engineering and Networks Laboratory Hardware-Software Codesign 1. Introduction Lothar Thiele
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Computer Engineeringand Networks Laboratory
Hardware-Software Codesign
1. Introduction
Lothar Thiele
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ContentsWhat is an Embedded System ?
Levels of Abstraction in Electronic System Design
Typical Design Flow of Hardware-Software Systems
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Main reason for buying is not information processing
Embedded systems (ES) = information processing systems embedded into a larger product
Examples:
Embedded Systems
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Embedded Systems
external process
embedded system
human interface
sensors, actuators
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Parallel and Distributed Target Platforms
ACC
ABSESP
ASR
enginecontrol powertrain
control
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Examples
AMD multicore RYZEN
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Examples
Intel Xeon Phi 7290(8 Billion transistors,14nm technology, ~ 650mm2 die area,
1.5 GHZ clock frequency)
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Embedded Multicore ExampleRecent development: Specialize multicore processors towards real-time processing
and low power consumption Target domains:
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Multiprocessor systems-on-a-chip (MPSoCs)Samsung Galaxy S6
– Exynos 7420 System on a Chip (SoC)– 8 ARM Cortex processing cores
(4 x A57, 4 x A53)– 30 nanometer: transistor gate width
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Multiprocessor systems-on-a-chip (MPSoCs)Samsung Galaxy S6
– Exynos 7420 System on a Chip (SoC)– 8 ARM Cortex processing cores
(4 x A57, 4 x A53)– 30 nanometer: transistor gate width
Exynos 5422
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Zero Power Systems and Sensors
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Zero Power Systems and Sensors
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 48, NO. 1, JANUARY 2013
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ComparisonEmbedded Systems Few applications that are
known at design-time. Not programmable by end
user. Fixed run-time requirements
(additional computing power not useful).
Criteria: • cost• power consumption• predictability• meeting time bounds• …
General Purpose Computing Broad class of applications.
Programmable by end user.
Faster in average is better.
Criteria:• cost• average speed
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Design ChallengesChallenges in the design of embedded systems increasing application complexity even in standard and large
volume products• mixture of event driven and data flow tasks (see next chapter) • examples: multimedia, automotive, mobile communication
increasing target system complexity• mixture of different technologies and processor types• large systems-on-a-chip combining components from different
sources, distributed system implementations
numerous constraints and design objectives• examples: cost, power consumption, timing constraints, temperature
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Implementation Alternatives
PerformancePower Efficiency Flexibility
Application-specific integrated circuits (ASICs)
Application-specific instruction set processors (ASIPs)
• Microcontroller• DSPs (digital signal processors)
General-purpose processors
Programmable hardware
• FPGA (field-programmable gate arrays)
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ContentsWhat is an Embedded System ?
Levels of Abstraction in Electronic System Design
Typical Design Flow of Hardware-Software Systems
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Abstraction, Models and SynthesisModel Formal description of selected properties of a system or subsystem A model consists of data and associated methods
Classification of models Degree of abstraction, granularity
• hardware: system, architecture, logic, transistor, • software: module, block/class, function/method, ...
View• behavior, structural, physical
Synthesis Linking adjacent levels of abstraction (refinement) Stepwise adding of structural information
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Structure
Behavior
Levels of Abstractions
SystemArchitecture
RTL
Process/Module
Function SW HW
Object Code
Gate-level modelsSwitch-level modelsCircuit-level modelsDevice-level modelsLayout models
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ContentsWhat is an Embedded System ?
Levels of Abstraction in Electronic System Design
Typical Design Flow of Hardware-Software Systems
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SW-Compilation HW-Synthesis
System DesignSpecification
System Synthesis
Machine Code Net lists
Estimation
Instruction Set
IntellectualProp. Block
IntellectualProp. Code
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Fixed Processor Architecture
SW-Compilation HW-Synthesis
Specification
System Synthesis
Machine Code Net lists
Estimation
Instruction Set
IntellectualProp. Block
IntellectualProp. Code
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Application Specific HW Block
SW-Compilation HW-Synthesis
Specification
System Synthesis
Machine Code Net lists
Estimation
Instruction Set
IntellectualProp. Block
IntellectualProp. Code
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Application-Specific Instruction Set Processor
SW-Compilation HW-Synthesis
Specification
System Synthesis
Machine Code Net lists
Estimation
Instruction Set
IntellectualProp. Block
IntellectualProp. Code
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The System Synthesis Problem
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HW/SW Mapping and SchedulingHardware/software mappingPartitioning of system function to programmable components (software), hard-wired or parameterized components (hardware) or application specific instruction set processors.
Similarity to scheduling and load distribution problem in real-time operating systems: time constraints, context switch and context switch overhead,
process synchronization and communication Differences to real-time operating systems: larger design space with very different solutions high optimization requirements (motivation for hardware design) underlying hardware is not fixed
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HW/SW Mapping and Scheduling
dedicated HWcomponents
P1
P3
P2P4
SW(processors)
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EstimationThe principle of synthesis based on abstraction only makes sense if there are powerful estimation methods available: Estimate properties of the next layer(s) of abstraction. Design decisions are based on these estimated properties: If
the estimation is not correct (or not accurate enough), the design will be sub-optimal or even not working correctly.
Design SpaceExploration
TimelineofDesign
Design SpaceExploration
Design SpaceExploration
Estimation oflower layerproperties
highabstraction
lowabstraction
...
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Review: Course SynopsisSpecification and Models of Computation (Section 2) State-Charts Kahn Process Networks
System Design Mapping (Section 3) Partitioning (Section 4) Multi-Criteria Optimization (Section 5) Design Space Exploration (Section 7)
Estimation Simulation-based Methods (Section 6) Performance Estimation (Section 8) Worst-Case Execution Time Analysis (Section 9) Performance Analysis of Distributed Systems (Section 10) Thermal-aware Design (Section 11)
