Overview of Embedded Computing Systems

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Overview of Embedded Computing Systems

• ECE 253 Winter 2007
• Lecture 1
• Ryan Kastner
• January 17, 2007

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What is an Embedded Computing System?
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Example Embedded Computing Systems
Slide courtesy of Mani Srivastava?
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Chips Everywhere!
Slide courtesy of Alberto Sangiovanni-Vincentelli?
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More Embedded Systems
Camera-on-chip (Bell Labs)
Solar-power Wireless Sensor (Berkeley)
Slide courtesy of Mani Srivastava?
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Electronics and the Car

• More than 30 of the cost of a car is now in
  Electronics
• 90 of all innovations will be based on
  electronic systems

Slide courtesy of Alberto Sangiovanni-Vincentelli?
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More Examples...

• Signal processing systems
• radar, sonar, real-time video, set-top boxes, DVD
  players, medical equipment, residential gateways
• Mission critical systems
• avionics, space-craft control, nuclear plant
  control
• Distributed control
• network routers switches, mass transit systems,
  elevators in large buildings
• Small systems
• cellular phones, pagers, home appliances, toys,
  smart cards, MP3 players, PDAs, digital cameras
  and camcorders, sensors, smart badges

Slide courtesy of Mani Srivastava?
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Typical Characteristics of Embedded Systems

• Part of a larger system
• not a computer with keyboard, display, etc.
• HW SW do application-specific function not
  G.P.
• application is known a priori
• but definition and development concurrent
• Some degree of re-programmability is essential
• flexibility in upgrading, bug fixing, product
  differentiation, product customization
• Interact (sense, manipulate, communicate) with
  the external world
• Never terminate (ideally) fundamentally
  different from TM
• Operation is time constrained latency,
  throughput
• Other constraints power, size, weight, heat,
  reliability etc.
• Increasingly high-performance (DSP) networked

Slide courtesy of Mani Srivastava?
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Key Recent Trends

• Increasing computation demands
• e.g. multimedia processing in set-top boxes, HDTV
• Increasingly networked
• to eliminate host, and remotely monitor/debug
• embedded Web servers
• e.g. IQEye camera
• e.g. Mercedes car with web server
• embedded Java virtual machines
• e.g. Java ring, smart cards, printers
• cameras, disks etc. that sit directly on networks
• Increasing need for flexibility
• time-to-market under ever changing standards!
• Need careful co-design of h/w s/w!

Slide courtesy of Mani Srivastava?
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Why do we care? Some Market Tidbits...

• Specialized devices and information appliances
  are replacing the generalist PC
• variety of forms set-top boxes, fixed-screen
  phones, smart mobile phones, PDAs, NCs, etc.
• IDC predicted that by 2002 gt 50 of inter access
  devices will be such into appliances and not PCs
• In 1997, 96 of internet access devices sold in
  the US were PCs
• By 2004, unit shipments will exceed those of PCs
• Traditional systems becoming dependent on
  computation systems
• Modern cars up to 100 processors running
  complex software
• engine emissions control, stability traction
  control, diagnostics, gearless automatic
  transmission
• http//www.howstuffworks.com/car-computer.htm
• An indicator where are the CPUs being used?

Slide courtesy of Mani Srivastava?
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Where are the CPUs?

• Estimated 98 of 8 Billion CPUs produced in 2000
  used for embedded apps

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What are the Metrics to Optimize?
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Whats Important Shifts in Technology Metrics

• Display (human-computer interface)
• More ubiquitous I/Os (e.g., MEMS sensors
  actuators) and modalities (speech, vision, image)
• How to Quantify?
• Connectivity (computer-computer interface)
• Not bandwidth but scaled ubiquity
• Million accesses (wired and wireless) per day
• Computing (processing capacity)
• Unbounded capacity utility functionality (very
  high mean time to unavailable, gracefully
  degraded capability acceptable)

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Whats Important Shifts in User/Applications
Metrics

• Cost Human Effort
• Save time
• Reduce effort
• The Next Power Tools
• Leveraging other peoples effort/expertise
• e.g., What did Dave read about disk prices?
• e.g., What did people who buy this book also
  buy?

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What kind of processor?
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Traditional Software Embedded Systems CPU
RTOS
Slide courtesy of Mani Srivastava?
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Many Types of Programmable Processors

• Past
• Microprocessor
• Microcontroller
• DSP
• Graphics Processor

• Now / Future
• Network Processor
• Sensor Processor
• Cryptoprocessor
• Game Processor
• Wearable Processor
• Mobile Processor

Slide courtesy of Mani Srivastava?
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Example Network Processor

• Good News
• Processor Power
• 2 years - 3 X
• Better News
• Optical Bandwidth
• 2 years - 10 X
• Bad News
• Handling increased complexity

Routing Switches Firewall Boxes Traffic
Shapers Aggregation Nodes Edge Routers Media
Servers
Slide courtesy of Mani Srivastava?
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Application-Specific Instruction Processors
(ASIPs)

• Processors with instruction-sets tailored to
  specific applications or application domains
• instruction-set generation as part of synthesis
• e.g. Tensilica
• Pluses
• customization yields lower area, power etc.
• Minuses
• higher h/w s/w development overhead
• design, compilers, debuggers
• higher time to market

Slide courtesy of Mani Srivastava?
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Traditional Hardware Embedded Systems ASIC
ASIC Features Area 4.6 mm x 5.1 mm Speed 20 MHz
_at_ 10 Mcps Technology HP 0.5 mm Power 16 mW -
120 mW (mode dependent) _at_ 20 MHz, 3.3 V Avg.
Acquisition Time 10 ms to 300 ms

• A direct sequence spread spectrum (DSSS) receiver
  ASIC

Slide courtesy of Mani Srivastava?
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Reconfigurable Hardware
Main Entry configure Pronunciation
kn-'fi-gyr Function transitive verb to set
up for operation especially in a particular
way
Main Entry re- Function prefix 1 again anew
ltretellgt 2 back backward ltrecallgt
KEY ADVANTAGE Performance of Hardware,
Flexibility of Software
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FPGA
CLB
Switchbox
Routing Channel
IOB
Routing Channel
Configuration Bit
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FPGA
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Programmable Logic
Tracks
Logic Element

• Each logic element outputs one data bit
• Interconnect programmable between elements
• Interconnect tracks grouped into channels

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Lookup Table (LUT)
2-LUT

• Program configuration bits for required
  functionality
• Computes any 2-input function

In Out 00 0 01 0 10 0 11 1
A
CA ? B
B
Configuration Bit 0
Configuration Bit 1
C
Configuration Bit 2
Configuration Bit 3
A
B
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Lookup Table (LUT)

• K-LUT -- K input lookup table
• Any function of K inputs by programming table
• Load bits into table
• 2N bits to describe functions
• gt different functions

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Lookup Table (LUT)
K-LUT (typical k4) w/ optional output
Flip-Flop
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Lookup Table (LUT)

• Single configuration bit for each
• LUT bit
• Interconnect point/option
• Flip-flop select

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Configurable Logic Block (CLB)
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Programmable Interconnect

• Interconnect architecture
• Fast local interconnect
• Horizontal and vertical lines of various lengths

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Switchbox Operation
Before Programming
After Programming

• 6 pass transistors per switchbox interconnect
  point
• Pass transistors act as programmable switches
• Pass transistor gates are driven by configuration
  memory cells

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Programmable Interconnect
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Programmable Interconnect
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Embedded Functional Units

• Fixed, fast multipliers
• MAC, Shifters, counters
• Hard/soft processor cores
• PowerPC
• Nios
• Microblaze
• Memory
• Block RAM
• Various sizes and distributions

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Embedded RAM

• Xilinx Block SelectRAM
• 18Kb dual-port RAM arranged in columns
• Altera TriMatrix Dual-Port RAM
• M512 512 x 1
• M4K 4096 x 1
• M-RAM 64K x 8

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Xilinx Virtex-II Pro

• 1 to 4 PowerPCs
• 4 to 16 multi-gigabit transceivers
• 12 to 216 multipliers
• 3,000 to 50,000 logic cells
• 200k to 4M bits RAM
• 204 to 852 I/Os

• Up to 16 serial transceivers
• 622 Mbps to 3.125 Gbps

PowerPCs
Logic cells
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Altera Stratix
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Modern Embedded Systems?

• Embedded systems employ a combination of
• application-specific h/w (boards, ASICs, FPGAs
  etc.)
• performance, low power
• s/w on prog. processors DSPs, ?controllers etc.
• flexibility, complexity
• mechanical transducers and actuators

Slide courtesy of Mani Srivastava?
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Complexity and Heterogeneity
controller processes
control panel
Real-time OS
ASIC
?controller
UI processes
DSP Assembly Code
Programmable DSP
Programmable DSP
DSP Assembly Code
CODEC
Dual-ported RAM

• Heterogeneity within H/W S/W parts as well
• S/W control oriented, DSP oriented
• H/W ASICs, COTS ICs

Slide courtesy of Mani Srivastava?
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Handling Heterogeneity
Slide courtesy of Edward Lee?
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Increasingly on the Same Chip System on a Chip
(SOC)
Slide courtesy of Mani Srivastava?
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Industrial Structure Shift (from Sony)
Slide courtesy of Mani Srivastava?
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Reconfigurable SoC
Other Examples Atmels FPSLIC(AVR
FPGA) Alteras Nios(configurable RISC on a PLD)

• Triscends A7 CSoC

Slide courtesy of Mani Srivastava?
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Many Implementation Choices

• Microprocessors
• Domain-specific processors
• DSP
• Network processors
• Microcontrollers
• ASIPs
• Reconfigurable SoC
• FPGA
• Gatearray
• ASIC

Speed
Power
Cost
High Low Volume
Slide courtesy of Mani Srivastava?
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Hardware vs. Software Modules

• Hardware functionality implemented via a custom
  architecture (e.g. datapath FSM)
• Software functionality implemented in software
  on a programmable processor
• Key differences
• Multiplexing
• software modules multiplexed with others on a
  processor
• e.g. using an OS
• hardware modules are typically mapped
  individually on dedicated hardware
• Concurrency
• processors usually have one thread of control
• dedicated hardware often has concurrent datapaths

Slide courtesy of Mani Srivastava?
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Hardware-Software Architecture

• A significant part of the problem is deciding
  which parts should be in software on programmable
  processors, and which in specialized hardware
• Today
• Ad hoc approaches based on earlier experience
  with similar products, on manual design
• HW-SW partitioning decided at the beginning, and
  then designs proceed separately

Slide courtesy of Mani Srivastava?
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Embedded System Design

• CAD tools take care of hardware fairly well
• Although a productivity gap emerging
• But, software is a different story
• HLLs such as C help, but cant cope with
  complexity and performance constraints
• Holy Grail for Tools People H/W-like synthesis
  verification from a behavior description of the
  whole system at a high level of abstraction using
  formal computation models

Slide courtesy of Mani Srivastava?
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Productivity Gap in Hardware Design
A growing gap between design complexity and
design productivity
Slide courtesy of Alberto Sangiovanni-Vincentelli?
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Situation Worse in S/W
DoD Embedded System Costs
Billion /Year
Slide courtesy of Mani Srivastava?
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Embedded System Design from a Design Technology
Perspective

• Intertwined subtasks
• Specification/modeling
• H/W S/W partitioning
• Scheduling resource allocations
• H/W S/W implementation
• Verification debugging
• Crucial is the co-design and joint optimization
  of hardware and software

Slide courtesy of Mani Srivastava?
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Embedded System Design Flow

• Modeling
• the system to be designed, and experimenting
  with algorithms involved
• Refining (or partitioning)
• the function to be implemented into smaller,
  interacting pieces
• HW-SW partitioning Allocating
• elements in the refined model to either (1) HW
  units, or (2) SW running on custom hardware or a
  suitable programmable processor.
• Scheduling
• the times at which the functions are executed.
  This is important when several modules in the
  partition share a single hardware unit.
• Mapping (Implementing)
• a functional description into (1) software that
  runs on a processor or (2) a collection of
  custom, semi-custom, or commodity HW.

Slide courtesy of Mani Srivastava?
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On-going Paradigm Shift in Embedded System Design

• Change in business model due to SoCs
• Currently many IC companies have a chance to sell
  devices for a single board
• In future, a single vendor will create a
  System-on-Chip
• But, how will it have knowledge of all the
  domains?
• Component-based design
• Components encapsulate the intellectual property
• Platforms
• Integrated HW/SW/IP
• Application focus
• Rapid low-cost customization

Slide courtesy of Mani Srivastava?
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IP-based Design
Slide courtesy of Mani Srivastava?
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Map from Behavior to Architecture
Slide courtesy of Mani Srivastava?
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Behavior Vs. Architecture
Performance models Emb. SW, comm. and comp.
resources
Models of Computation
1
HW/SW partitioning, Scheduling
2
System Behavior
System Architecture
Mapping
Behavior Simulation
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SW estimation
Performance Simulation
Synthesis
Communication Refinement
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Flow To Implementation
Slide courtesy of Alberto Sangiovanni-Vincentelli?
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Course Plan

• Design Specification
• Models of Computation
• Design Languages
• Architecture optimization
• HW/SW partitioning
• Hardware compilation
• Embedded System Synthesis

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Class Projects