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Embedded Systems Design


digital enabling technology is hidden inside the product such as TV remote ... embedded processor for scanning the keys and sending the data to the motherboard ... – PowerPoint PPT presentation

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Title: Embedded Systems Design

Embedded Systems Design
  • 52.360

What is an embedded system ?
  • 80 of all processors currently sold are used in
    embedded systems
  • digital enabling technology is hidden inside the
    product such as TV remote control or automotive
    control module
  • even PCs have embedded microprocessors - the
    keyboard will include an embedded processor for
    scanning the keys and sending the data to the
  • highly integrated digital technology provides
    advantages processing power, cost, size,

What is an embedded system ?
  • A large car may have 50 microprocessors
  • engine management systems
  • anti-lock brakes
  • transmission with electronic traction control
  • electronic gearboxes
  • airbag systems and other safety aids
  • air-conditioning etc
  • A washing machine may have a microprocessor based
    control unit
  • motor power control for pump, wash and spin
  • wash program control timing

What is an embedded system ?
  • Mobile phones contain more computing power than a
    desktop computer had a few years ago
  • Many toys and domestic appliances use
    microprocessor control
  • the cheapest microprocessor will cost maybe 30
  • the word control is at the heart of many
    embedded applications
  • for many systems the goal is to control a
    physical system (temperature, motion, audio..)
    using a variety of user/sensory inputs

What is an embedded system ?
  • Dedicated to controlling a specific device or
    function - sometimes with real-time constraints
  • Self-starting (no human intervention required).
    The user does not know whether there is a
    microprocessor or dedicated electronic hardware
  • not designed to be programmed by a user in the
    same way a PC is
  • Self-contained, with the program( and any OS)
    stored in some non-volatile memory

History ...
  • Microprocessor invented as a programmable
    replacement for calculator chips in the late 70s
  • up till then, control systems using digital
    technology utilised individual integrated circuit
  • many chips required to form an adder function..
  • then an adder became available on one chip -
    providing higher integration levels - smaller
    circuit boards
  • then a complete calculator functionality on one
    chip - even higher integration

History ...
  • So calculator was now low cost..but every change
    to the functionality required a new chip to be
    designed and created
  • what was needed was a more flexible device with
    some re-programmability inside it
  • a chip which took data in, processed it and sent
    it out again..
  • so instead of silicon engineers having to revise
    gate-level circuits and create new chips, the
    user of the chip could create a new wider range
    of products by changing the program code.

A Birth in the family.
  • The microprocessor was born, providing
    flexibility and low-cost
  • The goal is always less cost and more
  • the same embedded control board can be used for a
    range of products ( some functions or interfaces
    may not even be used)
  • the software can be changed or upgraded and can
    have different versions for different
  • the cost of production per unit can be lowered by
    using a large production run of the same hardware

More benefits.
  • Even if hardware is not re-usable the
    time-to-market advantage is clear and important
  • consider the rapid evolution of domestic
  • VCRs, televisions and microwave cookers need
    control panels/timers. These can be designed and
    taken to production quicker using the
    highly-integrated functionality of
    microcontrollers to form the heart of the system
  • Other systems (machine tools, telephone
    switchgear...) can have software upgrades but
    utilise existing embedded hardware

The benefits just keep coming...
  • Many systems which would have required expensive
    hardware upgrades in the past now need only
    software changes
  • this can sometimes be done remotely, using
    communication links
  • mechanical systems can be more effectively
    controlled by microprocessor
  • sensor derived data can lead to more effective
    control, thus reducing mechanical wear
  • diagnostics are available

Embedded Systems some areas of exploitation
Consumer Electronics
Embedded Systems
Space Exploration
Industrial Control
Embedded Systems a few examples
Engine Management
Lift Controllers
Microwave Ovens
Answering Machines
Embedded Systems
Robot Controllers
Navigation Systems
An engine management system...
  • Embedded microprocessor controls fuel mix and
  • control software considers accelerator position,
    temperature and other factors
  • engine is controlled efficiently
  • different configurations can be supplied with
    emphasis on power, torque or fuel-efficiency
  • can even compensate for component wear (if
    sensory data is available)
  • can provide driver with information

Dont try this at home.
  • Hackers get everywhere !
  • There is an expanding market for chipped engine
    management units
  • third-party companies modify the software that is
    used by the control unit ( using inside
    information) to provide more power or torque.
  • Can lead to dramatic changes in the performance
    of the car
  • this may invalidate your guarantee (
  • this may be very unsafe ( (
  • may infringe the original manufacturers
    intellectual property rights(IPR)

Embedded Systems..smaller and cheaper
  • Tamagochi (electronic pets)

Scenes from a small life.
Itll happen to us all...
Cost advantage...
  • These devices start at a cost of only 3
  • think about all the parts required
  • casing
  • buttons
  • LCD display
  • embedded microprocessor with program
  • circuit board
  • battery
  • packaging
  • the manufacturer will wish to produce the units
    for a third of the retail price

About IPR
  • Programs are expensive to create. Hardware and
    software design knowledge is what gives a company
    its competitive edge.
  • A hardware design may be created with only
    off-the-shelf parts so it can be difficult to
    protect the IPR. Competitors can get a board,
    trace the printed-circuit and if they know what
    the components are, can reproduce the board
  • some companies remove the markings from chips to
    make them anonymous

Embedded software can resist detection...
  • Some embedded software is placed in a
    PROM(programmable read only memory) external to
    the microprocessor
  • this could be copied if the PROM is unsoldered
    from the board and read in another circuit or
    PROM programmer (
  • Software can be programmed into PROM internal to
    the microprocessor. It is invisible and usually
    impossible to access. The IPR is protected )

Embedded Engineering Systems
  • Certain logical and temporal demands are placed
    on many of these systems
  • they react to sensory information
  • if temperature gt 40oC then ..
  • they may have strict deadlines
  • sampling must be undertaken 200 times/second
  • from the occurrence of a comms message a reply
    must be sent within 1mS
  • the stepping motor must be advanced 500
    steps/second maximum with acceleration and
    deceleration ramps

Embedded Engineering Systems
  • may be complex systems, heavily event driven
  • events generated by timers, sensors,
    user-controls and peripheral devices ( comms
    ports, vision systems)
  • Systems will be engineered with cost, size,
    weight, robustness and reliability constraints
  • may required specialised operating systems and
    programming languages
  • (pSOS, VxWorks, OS/9 are examples of real-time
    operating systems)

Embedded Engineering Systems
  • (Ada is an example of a multitasking language. C
    is inherently single-threaded but can be extended
    to multitasking capability using a library of
    calls to a multitasking operating system)
  • may require the developer to have a knowledge of
    the hardware/software boundary
  • needs knowledge of internal peripheral chip
    organisation, taken from data-sheets -
    addressing, control/data register configuration,
    timing issues
  • may require specialist development equipment such
    as emulators and logic analysers
  • emulators can trace and store processor/program
  • logic analysers can capture hardware signal

Embedded Systems environment
  • Industrial embedded systems have special problems
    to cope with
  • electrical noise in the environment
  • ( factory automation and automotive systems have
    to cope with high levels of electrical noise
    emissions )
  • wide temperature fluctuations
  • high levels of mechanical vibration
  • fluctuating humidity levels
  • liquids and gases in the environment
  • require specially ruggedised equipment
  • standard Personal Computers not suitable

Real-Time example Process Control
Controlled Gas Flow
Gas Flow Control
Process Control
A valve is an example of an Actuator. It moves in
response to electrical stimuli
A Transducer generates an electrical signal
proportional to the physical quantity
being measured
Temperature Transducer (sensor)
Chemicals and materials
Manufacturing Systems
Parts Movement
Machine Tools
Embedded Computer(s)
Embedded Systems are often Real-Time
  • Real-time systems can be categorised
  • hard real-time systems have absolute response
    times. If they are not met the system has failed
  • flight control systems, power-station control
  • soft real-time systems do not have such stringent
    deadlines and the occasional missed deadline is
    not critical
  • some systems will have both types of deadlines
  • a soft deadline 0f 100ms (for optimal response)
    and a hard deadline of 800mS (system failure if
    there is no response by this time)

An overview.
Control Algorithms
I/O System
Engineering System
Data Logging and processing
User Controls
Data Retrieval and display
Storage devices
Remote Devices
User Interfacing
Embedded Systems components
Storage Peripherals
Real Time Clock
Frequency Generators
Pulse-width Modulators
Serial Peripheral Interfaces
Embedded Systems
Comms Interfaces
Display Interfaces
Analogue I/O
Parallel I/O
Embedded Systems Two examples in one
Algorithms for digital control
Embedded Processor board
Engineering System
IR Communications
Data Retrieval and display
User Interface
User Interfaces
Real Time Embedded Systems Characteristics
  • Can be large and complex
  • require extensive maintenance
  • systems must be extensible because of change and
    evolution in the application environment
  • Can be small and compact
  • zero maintenance would be ideal
  • we dont want a software update for our
    washing-machine or video recorder firmware
    (non-changeable software in ROM/PROM)

Real Time Characteristics
  • Can involve complex control algorithms
  • mathematical modelling
  • feedback and feed-forward systems

Control Output
Feedback (position, velocity, acceleration,
Real Time Characteristics
Control Output
Parallel I/O
Actuators/ sensors
Parallel I/O
Computerised Control
Real Time Characteristics
  • Reliability and Safety issues important
  • system designs must reflect the nature of their
    application environment
  • autoteller machines, medical equipment, chemical
    control systems, aeronautic systems
  • fail-safe systems and multiple redundant systems
    may be implemented
  • human error should be minimised
  • If possible the computer system should always
    double-check decisions made by humans

Real Time Characteristics
  • Many different real-world elements exist at the
    same time
  • motors, conveyance-systems, sensors, displays,
    user-controls, databases
  • will require sufficient computing power to allow
    all deadlines to be met
  • can be widely geographically distributed
  • may require distributed computer systems or
    multiprocessor systems

Real Time Characteristics Software
  • Require a software structure which clearly
    represents the concurrency and parallelism
    present in the real world
  • Ideally we should use a software methodologies
    and languages which can express concurrency
    rather than use programmer-invented schemes
  • Why ?
  • We wish to move the programmers awareness and
    effort away from low-level structures which are
    not directly related to the application level
  • Less obscure solutions, easier to validate
    correctness, easier analysis/design, easier
    testing, easier maintenance

Real Time Characteristics Software
  • Requirement for a software structure which
    clearly represents the time-related aspects of
    system behaviour
  • programs must be logically and temporally correct
    under ALL conditions. This may mean basing
    processor loading on worst-case behaviour so
    that it still meets deadlines predictably under
    all conditions
  • need to meet deadlines
  • times at which actions are to be performed
  • when they have to be completed
  • respond to situations when all the timing
    requirements cannot be met or the timing changes
    dynamically due to system re-configuration

Real Time Characteristics Software
  • Example real-time requirements
  • sample (at certain times) at a given sampling
  • sample data from sensor between 8.00 - 23.00 at
    200 Hz
  • react to certain data-patterns within a certain
    time-scale (deadline)
  • Therefore we must have a predictable behavioural
    response from the computer system to the sampled
    data if we wish to meet the deadline
  • example In a gas control system, if pressure is
    suddenly lost then there is a requirement to
    isolate part of the supply network within a
    finite time

Characteristics Interaction with hardware
  • The nature of embedded systems is such that
    computer will need to interact with the outside
    world using peripheral devices
  • software interaction with the peripherals
    requires the program to be able to address the
    peripheral hardware interface devices
  • peripheral interface chips will have addressable
    locations for reading/writing control/status/data
  • interface chips may generate interrupts for the
    processor indicating that certain operations have
    taken place or an error condition has arisen

Characteristics Interaction with hardware
Characteristics Efficient Implementation
  • efficiency of execution means that the programmer
    cannot always use the highest-level of
  • the highest level abstraction may take extra
    execution time which may be excessive for a
    particular application
  • the programmer must be aware of the cost of
    particular software operations
  • if a response to an event is required within 20
    microseconds then it is no good using a
    high-level software feature which takes 40

Embedded systems software
  • We will return later to the subject of software
    for embedded systems
  • multitasking scheduling
  • real-time kernels
  • languages
  • communication
  • synchronisation
  • mutual exclusion
  • I/O drivers and hardware interaction
  • prioritisation

Back to hardware..
  • First we have an introduction to the hardware
    contained in embedded systems
  • we will start by a brief examination of digital
    signal processing and see how analogue electronic
    systems can be replaced by digital systems.

Digital can replace analogue
  • Increasing levels of processor power allow high
    performance applications to be performed
    digitally - digital signal processing
  • take an example of an analogue filter required to
    remove noise and other high frequency components
    from a sensor signal


Analogue components
  • Analogue components work on a continuous basis,
    with infinite values within the range they work
  • can implement sophisticated mathematical
  • they are cheap and can form many different
  • are extremely fast ( can easily process GHz rate
  • but suffer (to a small extent) from
  • component ageing
  • drift (with temperature for instance)
  • noise pickup
  • also
  • fairly fixed functionality once the circuit is

Digital signal processing (DSP)
  • The digital equivalent of the filter is a fast
    processor which can sample the input signal,
    process it and output the signal sufficiently
    often to maintain similar accuracy, resolution
    and frequency response
  • it must provide the same function as the original
    analogue implementation
  • but there is a major difference
  • since the digital version must sample the input
    then this is not a continuous system - rather, it
    is a discrete system.

Digital signal processing
  • The implementation of the filter function
    requires an equation of the form
  • where C comes from a coefficient table and the X
    values are sampled analogue input values
  • this means there must be a set of multiply and
    accumulate operations executed for every sample
  • we must continuously sample, execute the
    instructions for the equation, then output the
    new value

Time analysis for a digital filter.
Process n instructions
  • The higher the input bandwidth, the higher the
    sampling rate needs to be to collect sufficient
  • the higher the sampling rate, the faster the
    processor has to be to execute the n instructions
    between samples

Sampling power required.
  • For DSP applications the sampling speed is
    usually twice the frequency of the highest
    frequency signal signal being processed
  • Nyquist's theorem A theorem, developed by H.
    Nyquist, which states that an analogue signal
    waveform may be uniquely reconstructed, without
    error, from samples taken at equal time
    intervals. The sampling rate must be equal to, or
    greater than, twice the highest frequency
    component in the analogue signal.

Processing power required.
  • Lets look at options for a DSP application

Processing power and sampling rate...
  • The faster the sampling rate the more power is
  • For example to achieve a 1MHz sampling
    frequency, a 10 MIPS processor is required whose
    instruction set is powerful enough to complete
    the required processing in under 10 instructions
  • from Nyquists theorem, this would allow us to
    process signals up to 500kHz
  • specialised DSP processors with an architecture
    and special instructions geared to the types of
    operations required by signal processing

Why use digital signal processors ?
  • Given the complexity involved, why do we bother
    using DSP technology ?
  • No component ageing
  • low drift ( apart form A/D which requires careful
    printed-circuit layout and clean power supply)
  • no adjustments required
  • high noise immunity ( we are using all digital
  • small amounts of analogue noise voltage have no
    effect on digital logic devices. In analogue
    components(especially amplifiers and adders)
    noise can be a problem.

Why use digital signal processors ?
  • Can include extra self-testing features. This
    helps at production-time and also for maintenance
    and fault-finding
  • Software is the ultimately flexible tool. Just by
    changing a few coefficients we can have a
    completely different filter for example. We can
    parameterise the software to allow a wide range
    of functionality with the same hardware.
  • DSP can be performed by ordinary microprocessors,
    but the general-purpose nature of their
    instruction-set limits their performance and thus
    frequency response.
  • We will look at a representative DSP device later

Embedded system components Processor
  • does it provide required processing-power ?
  • Tasks can be under-specified or under-estimated
  • system evolves during development and outgrows
    the processing power
  • inadequate benchmarking has been performed
  • for instance, a test program which is inadequate
    may run only in the processor cache and thus make
    the processor look very impressive. The actual
    programs may not manage to utilise the cache in
    the same way and execute mainly out of cache,
    leading to a slower system than was anticipated

Embedded system components Processor
  • Software overheads for high-level-languages(HLLs)
    Operating systems and heavily loaded interrupts
    may tax the processor
  • the overall cost of a processor is not just the
  • How much power does it consume ?
  • Heat-sink required ?
  • Space on PCB required
  • other support chips required ?
  • What is its availability and delivery time ?
  • Engineers experience of processor / learning
  • price of software tools ( compilers, debuggers,
    emulators, operating systems)

Embedded system components Memory
  • Software storage -ROM and PROM
  • on-chip Read Only Memory (ROM)
  • external Programmable ROM (PROM)
  • development versions of these are called Erasable
  • Contains initialisation (bootstrap) code and
    application code
  • External RAM is used for data storage
  • microcontrollers usually contain a small amount
    of internal RAM as well as ROM storage - maybe as
    little as 256 bytes up to a few Ks. Some
    applications are engineered to use just on-chip
    RAM as an economy. External RAM may cost as much
    as a processor

Embedded system components Memory
  • Non-volatile memory devices can be programmed as
    a system is powered-up and executing. The stored
    data is retained when the system is powered-down
  • battery-backed-up RAM modules
  • non-powered non-volatile RAM devices
  • Flash memory devices - high density (1Mbyte
    upwards in each device) - can be used to create
    Flash-disks (totally semiconductor non-volatile
    file storage)
  • many microcontrollers may include an area of
    non-volatile memory internally

Embedded system components Peripherals
  • interfaces for analogue peripheral devices

Input conditioning
Motors, actuators, pumps, temperature control,
position-control, audio, video etc
Output conditioning
Embedded system components Peripherals
  • Example a PWM motor controller
  • inputs are
  • demanded speed - user input
  • actual speed - sensor output
  • output is
  • pulse-width modulated (PWM) waveform to control
    power-switching to the motor

PWM Waveform
Software to implement motor control
Power amplifier
A/D converter
Speed Sensor (tachometer) output
Parallel interface
Embedded system components Peripherals
  • Main types of peripherals
  • binary outputs - simple external pins which can
    output a 1 or a 0 (5V or 0V approx.).Often
    grouped together to form parallel ports where a
    group of bits can be input or output
    simultaneously. Once a bit is set, the value
    remains because it uses a latching flip-flop
  • serial outputs - send and receive data using a
    transmit(tx) pin and a receive(rx) pin on a chip.
    Parallel data is written to a register and the
    serial port logic automatically sends it
    serially, bit by bit, out on the tx pin at a
    program selectable rate. Status register
    information is available to be read by a program
    and error information is also available.

Embedded system components Peripherals
  • Analogue interfaces the real world often
    provides continuous analogue information whereas
    the digital world works with discrete values.
    Conversion circuits are required
  • Displays simple seven-segment
    light-emitting-diode(LED) displays, individual
    LEDs, liquid-crystal-displays(LCD) of various
    forms including graphic and alpha-numeric,
    monitors and other display technologies
  • Time related values counter-timer devices allow
    rate-generation, PWM, single-shot pulse(one pulse
    of deterministic length) and also allow
    measurement of time and rate from externally
    generated pulse sources.

  • Microcontrollers are self-contained systems with
    processor, memory and peripherals
  • in many cases an application can be created just
    by adding software
  • in other cases extra external memory (PROM, RAM)
    and other peripherals can be added while still
    utilising the internal functionality)
  • processors are often 8 or 16-bit stack-based
  • there are also cheap 4-bit processors available
  • usually a family of microcontrollers will have
    several variants with different or extra
    facilities added

(No Transcript)
  • Microcontroller will be available in several
  • devices for prototyping
  • programmer must be able to load code into the
  • Ultra-Violet(UV) erasable EPROM or electrically
    erasable(EEPROM) parts are used to store the
  • this replaces the ROM into which the program will
    be mask-programmed during a production-run of the
    processor (a volume of 2000 upwards may be
    required by the manufacturer before they will do

  • Internal non-volatile RAM (NVRAM)versions mean
    that a company can create a low-volume production
    run of a particular product with the program set
    into the NVRAM
  • NVRAM also permits customisation of the program
    if a number of variants of a product are required
  • One-time programmable(OTP) are available. These
    are cheaper than the PROM or EEPROM versions and
    can thus be used economically for low to medium
    volume production runs. They have a slight
    disadvantage in the cost of time/personnel to
    program them, but the flexibility outweighs this

Microcontrollers for high-volume product
  • Devices for high-volume production
  • Customer supplies software to chip manufacturer
  • manufacturer creates the masks which form the ROM
    of the device
  • these masks are used to form a new layer on
    partially completed silicon wafers (to reduce
    turnaround time)
  • costs are lowered
  • production time lowered (no chip programming to
    be done by the chip user)
  • but..

Microcontrollers for high-volume product
  • Minimum order must be placed based on the number
    of chips that a wafer-batch can produce
  • one-off tooling charge for creating the mask
  • software cannot be changed until another
    production run
  • there may already be parts in the production
    pipeline(packaging/testing etc) and these will
    have to be scrapped if a program needs changed
  • some customisation may be available in the form
    of different software modules being included in
    the ROM. Modules can be selected by a coded word
    read into a port of the microcontroller. A design
    could include extra external hardware to allow
    the code to be set for a particular product.

Expanded microcontroller mode
  • This very flexible mode allows the use of
    external RAM/ROM/other external devices where
    internal facilities are insufficient
  • there is is a resultant cost in the extra
    components and the non-availability of the ports
    used up by the external devices. However, many
    designs utilise this mode while still using the
    internal facilities

Data/address buses
  • There is very much a trend towards high levels of
    integration to put as many functions as possible
    inside a single chip
  • in earlier years people might use standard
    microprocessors (such as appear in
    workstations/PCs) and add external peripheral
    hardware. Foe example MC68020, 30 and 40. Intel
    80286,386.486, Pentium , Power-PC, MIPS
  • Now the latest processors are combined with many
    peripheral functions to form special purpose
    integrated processors. These are much more
    powerful than the small microcontrollers.

Board-based embedded systems
  • We have assumed so far that the hardware always
    needs to be designed, built and debugged before
    the product development can progress further.
    This process can delay a product for weeks or
    months depending on the board(s) complexity.
    There exist a range of levels of integration
  • One alternative is to use a board-based solution
    where already existing hardware boards are used.
    These are built to certain recognised standards
    (VME-bus interconnect for instance) and are
  • Main advantage is reduced workload (dont need
    expert hardware engineers), reduced time-scales
    and the availability of perhaps OS/software
    application modules. Good solution for low-volume
  • there is a higher cost and perhaps restricted
    functionality or unused functionality (not really
    a problem)

Board-based embedded systems
  • VME-bus rack system

Board-based embedded systems
  • A VME-bus card.

Embedded processors
  • Embedded processor evolution has closely followed
    that of standard microprocessors
  • better chip fabrication technology
  • higher transistor density - more transistors
  • lower power dissipation
  • smaller processor core leaves room for
    peripherals to be integrated onto chip
  • four basic architectures used
  • 8-bit
  • 16/32 bit complex instruction set (CISC)
  • Reduced Instruction Set (RISC)
  • Digital Signal Processor (DSP)

Embedded Microcontrollers are a big business
  • World-Wide Microcontroller Shipments (in
    millions of dollars)
  • '90 '91 '92 '93
    '94 '95 '96 '97 '98 '99
  • 4-bit 1,393 1,597 1,596 1,698 1,761 1,826
    1,849 1,881 1,856 1,816 1,757
  • 8-bit 2,077 2,615 2,862 3,703 4,689 5,634
    6,553 7,529 8,423 9,219 9,715
  • 16-bit 192 303 340 484 810
    1,170 1,628 2,191 2,969 3,678 4,405
  • World-Wide Microcontroller Shipments (in
  • '90 '91 '92 '93
    '94 '95 '96 '97 '98 '99
  • 4-bit 778 906 979 1036 1063 1110
    1100 1096 1064 1025 970
  • 8-bit 588 753 843 1073 1449 1803
    2123 2374 2556 2681 2700
  • 16-bit 22 38 45 59 106
    157 227 313 419 501 585

Embedded Microcontrollers are a big business
  • look back at the table
  • even the lowly 4-bit processor device is holding
    its own
  • what use is a 16-bit part in a toaster?
  • the 8-bit market just keeps growing, and will
    probably continue to grow. 8-bit devices account
    for over half of the market, and will eventually
    have a larger proportion.
  • All silicon manufacturer market their 8-bit
    processor range very aggressively because the
    market is worth billions of dollars world-wide

Electronics is the driving force...
  • Average Semiconductor Content per Passenger
    Automobile (in Dollars)
  • '90 '91 '92 '93 '94
    '95 '96 '97 '98 '99 '00
  • 595 634 712 905 1,068 1,237 1,339
    1,410 1,574 1,852 2,126

  • Source ICE - 1994
  • The automotive market is the most important
    single driving force in the microcontroller
    market, especially at it's high end.
  • Several microcontroller families were developed
    specifically for automotive applications and were
    subsequently modified to serve other embedded

Growing markets..
  • The automotive market is demanding. Electronics
    must operate under extreme temperatures and be
    able to withstand vibration, shock, and EMI. The
    electronics must be reliable, because a failure
    that causes an accident can (and does) result in
    multi-million dollar lawsuits.
  • Reliability standards are high - but because
    these electronics also compete in the consumer
    market - they have a low price tag.
  • Automotive is not the only market that is
  • DataQuest says that in the average North
    American's home there are 35 microcontrollers.
    By the year 2000 - that number will grow to 240.
    Consumer electronics is a booming business.

How do you choose ?
  • When deciding which devices to implement in a
    design, there are lots of things to consider
    besides who else is using these devices (and how
    many are they using).
  • Can I expect help when I am having problems?
  • What development tools are available and how much
    do they cost
  • What sort of documentation is available
    (reference manuals, application notes, books)?
  • Can I reduce prices by purchasing more devices
    at one manufacturer? That is, purchasing not only
    the microcontroller, but also peripherals (A/D,
    memory, voltage regulator, etc.) from one
  • Do they support one-time programmable(OTP),
    windowed devices, mask-programmable(at the chip
    manufacturer) parts?

Embedded processors - life cycle
  • Standard microprocessors have a life cycle..
  • they are released as high performance devices
  • over a period of 15 or more years they gradually
    become medium-to-low performance(comparatively
    speaking) as higher performance devices are
  • their life-cycle would naturally end here. They
    are no longer sold as standalone processors
  • The basic design continues to be used when the
    processor core has been utilised as the heart of
    a highly integrated device.

Embedded processors - life cycle
  • Take for example the Motorola M6800 - one of the
    early microprocessors released in 1975
  • a simple 8-bit architecture with 1Mhz clock speed
  • most of the instructions execute in 2 or 3 clock
  • no sophisticated architectural features
  • The 6800 had end-of-life in 1993. No new designs
    utilising 6800 would have been started for a
    number of years - but existing product production
    may have demanded the availability of the chip
  • However, there are over 200 MC6801/6805/68HC11
    microcontroller variants in production, utilising
    a processor architecture/instruction-set similar
    to the 6800 (speeds from 1MHz to 4MHz, 90 extra
    op-codes in HC11s )

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Embedded processors - floor-plan - 68HC11A8
Here is a Motorola MC68HC11A8 microcontroller
chip. Notice the small space taken by the CPU
against the space taken by all the other parts
integrated on the chip.
Embedded processors - floor-plan - 68HC11
Here is a Motorola MC68HC11E9 microcontroller
chip. More RAM and ROM on-chip means more space
given to these.
HC11A8 packaging
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HC11 registers
  • Although this looks like a primitive model the
    addressing modes enrich the functionality
  • many instructions can act directly on memory
    using the index registers as pointers
  • the A and B registers can also be manipulated as
    a single 16-bit data register (D reg) for add,
    subtract and shift operations. Multiply is still
    8-bit operands only
  • there is a dedicated stack pointer register
  • stack is used to provide local storage for
    functions and also hold return addresses for
    function calls and interrupts

Addressing memory...
  • When 8-bit microprocessors appeared in the
    1970s, memory was ..
  • expensive
  • only available in small sizes (256 bytes up to
  • applications were small
  • written in assembler before specialised compilers
    were written for the processors
  • the 64K address space offered by the processors
    seemed huge and would never be used up!
  • advent of high-level-languages(HLLs) and
    operating systems (like CP/M) increased memory
  • memory started to become a limitation

System Integrity
  • Simple architectures can be unpredictable in
    handling error conditions and limit the use of
    the processors to non-critical applications
  • software bug could cause data corruption
  • system crash
  • system hangs
  • system performs unforeseen operations !
  • There is no partitioning between programs and
    data within the architecture
  • an application could overwrite its program area
    using a corrupt pointer for example
  • in some architectures certain undocumented code
    sequences could put a machine into test mode !!!!!

Integrated Processors
  • These combine high performance processors
    together with specialised I/O facilities to form
    the basis of powerful but low chip-count systems
  • The processor core is usually an already proven
    design which has development facilities and
    software available
  • the MC683xx family contains a 68000 family core,
    timer systems, watchdogs, secondary RISC
    processor to handle specialised
    data-communication peripherals and also
    specialised timer systems
  • new versions are also available with a PowerPC
    processor core

Integrated Processor exampleMC68LC302
The main features of this device are outlined in
the next two pages. They are provided to indicate
the richness of functionality available within
highly integrated devices and are not to be
committed to your memory!
  • Features of MC68LC302
  • On-Chip Static 68000 Core supporting a 16- or
    8-Bit M68000 Family System
  • System Interface Bus Including
  • Independent Direct Memory Access (IDMA)
  • Interrupt Controller with Two Modes of Operation
  • Parallel Input/Output (I/O) Ports, Some with
    Interrupt Capability
  • On-Chip 1152-Byte Dual-Port RAM
  • Three Timers Including a Watchdog Timer
  • New Periodic Interrupt Timer (PIT)
  • Four Programmable Chip-Select Lines with
    Wait-State Generator Logic
  • Programmable Address Mapping of the Dual-Port RAM
    and IMP Registers (provides flexibility in
    designing the system memory map)
  • On-Chip Clock Generator with Output Signal
  • On-Chip PLL Allows Operation with 32 kHz or 4 MHz
  • Glue-less Interface to EPROM, SRAM, Flash EPROM,
    and EEPROM

  • Features of MC68LC302
  • Built-in communications processor (CP) Including
    a RISC Processor
  • Two independent full-duplex serial communications
    controllers (SCCs) supporting various protocols
  • High-Level/Synchronous Data Link Control
  • Universal Asynchronous Receiver Transmitter
  • Binary Synchronous Communication (BISYNC)
  • Autobaud Support and V.110 Rate Adaption
  • Four Serial DMA Channels for the Two SCCs
  • Flexible Physical Interface Accessible by SCCs
  • Motorola Interchip Digital Link (IDL)
  • General Circuit Interface (GCI, Also Known as
    IOM-2 1 )
  • Pulse Code Modulation (PCM) Highway Interface
  • Nonmultiplexed Serial Interface (NMSI)
    Implementing Standard Modem
  • SCP for Synchronous Communication
  • Two Serial Management Controllers (SMCs)
  • 100 Pin Thin Quad Flat Pack (TQFP) Packaging

Highly Integrated the benefits...
  • Functions which normally require external chips
    are now integrated inside one chip
  • save money
  • save board space (so its smaller and also
  • the more integrated, the higher the overall
    system reliability
  • as processor cores become mainstream, they can be
    included as the core of these integrated products
  • the latest versions of these Motorola integrated
    processors are using a 50MHz PowerPC processor
  • Buffering and low-level protocol management is
    performed by the specialised comms processor

Highly Integrated the benefits...
  • This particular device (MC68LC302 ) is a
    specialised communications device, so..
  • As the low level protocol code is actually
    implemented in microcode inside the comms
    co-processor, the main processor (68000 or
    PowerPC) is freed-up to take care of the
    higher-level layers of the protocols
  • Can cope with a combined bandwidth up to 2Mbits
    over three comms channels
  • also, chip select lines are available so these
    devices can be connected to external chips
    (EPROM, RAM etc) without the requirement for an
    external decoder.

Space saving before..
Glue logic - probably a PLD
Address decoder
Chip select lines
Standard processor
Address Bus. The data bus and other connections
are not shown
Space saving after..
Look..no glue logic required!
Chip select lines
Processor with built-in decoding for external
Address Bus. The data bus and other connections
are not shown
Digital signal Processors
  • In the strict sense of the term, digital signal
    processing refers to the electronic processing of
    signals such as sound, radio, and microwaves.
  • In practice, the same characteristics that make
    Digital Signal Processors (DSPs) so good at
    handling signals make them suitable for many
    other purposes, such as high-quality graphics
    processing and engineering simulations.
  • DSPs are essentially super fast number-crunchers
    and just about any application that involves
    rapid numeric processing is a candidate for
    digital signal processing.

Digital Signal Processors Overview
  • Like earlier advances in microprocessors and
    computer memories, digital signal processing is a
    foundation technology with the power to transform
    broad areas of the electronics industry. Its
    impact is being felt in applications as diverse
    as stereo systems, cars, personal computers, and
    cellular phones. In the next few years, digital
    signal processing will give rise to hundreds of
    new products and change what people expect from
  • Digital signal processing takes real-time,
    high-speed information, such as radio, sound or
    video signals, and manipulates it for a variety
    of purposes. Digital signal processing can
    restore vintage jazz recordings to their original
    clarity, erase the static from long-distance
    phone lines and enable satellites to pick out
    terrestrial objects as small as a golf ball.

Digital Signal Processors Overview
  • In cars, Digital Signal Processors (DSPs) create
    digital audio surround sound and are
    responsible for active suspension systems that
    adjust automatically to road conditions. In
    cellular phones, digital signal processing helps
    squeeze more conversations onto crowded airwaves
    and can scramble signals to thwart eavesdroppers.
    In multimedia computers, digital signal
    processing generates business communication at
    the users fingertips and professional audio
    sound in real time.
  • Once used primarily for academic research and
    futuristic military applications, digital signal
    processing has become a widely accessible
    commercial technology. In the last few years, a
    variety of high-performance, integrated DSPs
    have made digital signal processing technology
    easier and more affordable to use, particularly
    in low-end applications.

Digital Signal Processors Overview
  • Also, software and development tools are more
    available so equipment manufacturers are becoming
    experienced in the use of DSPs and sales are
    expanding rapidly.
  • The market for DSP chips is growing at twice the
    rate of the semiconductor industry as a whole,
    according to Forward Concepts of Tempe, Arizona.
    Over the next few years the digital signal
    processing business is expected to increase by 33
    percent annually, leading to an overall market of
    11 billion in 1999. About 4.5 billion of this
    will be for general purpose DSPs.
  • Specialist DSPs are available for applications
    such as audio processing where the DSP core is
    integrated with audio functionality (A/D, D/A,
    filters etc) on one chip

DSP Background
  • Started as specialist processors for digital
    signal processing algorithms
  • an example is a finite impulse response (FIR)
  • requires the setting-up of two tables, one
    containing sampled data, the other
    filter-coefficients that determine the filter
  • program then performs a series of repeated
    multiply and accumulates using values form the
  • the attainable bandwidth of the filter depends on
    the speed of these simple operations

Motorola DSP56002 DSP
  • This processor uses a DSP56000 core ( as
    described in Heath) and adds internal memory
    storage for program and data - lowering the
    system cost/complexity/size
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