Embedded Systems Design

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Embedded Systems Design

• 52.360

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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
  motherboard
• highly integrated digital technology provides
  advantages processing power, cost, size,
  time-to-market

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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

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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
  pence
• 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

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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
  inside
• 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

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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
  devices
• 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

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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.

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A Birth in the family.

• The microprocessor was born, providing
  flexibility and low-cost
• The goal is always less cost and more
  functionality
• 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
  applications
• the cost of production per unit can be lowered by
  using a large production run of the same hardware

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More benefits.

• Even if hardware is not re-usable the
  time-to-market advantage is clear and important
• consider the rapid evolution of domestic
  electronics
• 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

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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

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Embedded Systems some areas of exploitation
Medical
Telecomms
Avionics
Consumer Electronics
Embedded Systems
Space Exploration
Industrial Control
Automotive
Multimedia
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Embedded Systems a few examples
Engine Management
Lift Controllers
Microwave Ovens
Answering Machines
Embedded Systems
Robot Controllers
Navigation Systems
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An engine management system...

• Embedded microprocessor controls fuel mix and
  ignition
• 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

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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)

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Embedded Systems..smaller and cheaper

• Tamagochi (electronic pets)

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Scenes from a small life.
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Itll happen to us all...
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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

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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

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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 )

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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

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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)

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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
  activity
• logic analysers can capture hardware signal
  activity

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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

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Real-Time example Process Control
A/D
D/A
Controlled Gas Flow
Gas Flow Control
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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)
Valve
Stirrer
Chemicals and materials
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Manufacturing Systems
Manipulators
Parts Movement
Machine Tools
Embedded Computer(s)
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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)

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An overview.
Control Algorithms
I/O System
Engineering System
Data Logging and processing
Sensors
Actuators
User Controls
Displays
Data Retrieval and display
Storage devices
Communications
Remote Devices
User Interfacing
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Embedded Systems components
Storage Peripherals
Real Time Clock
Frequency Generators
Pulse-width Modulators
Processor(s)
Serial Peripheral Interfaces
Memories
Embedded Systems
Comms Interfaces
Counter/timers
Display Interfaces
Analogue I/O
Parallel I/O
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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
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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)

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Real Time Characteristics

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

Control Output
error
Demand
?
Controller
Plant
Feedback (position, velocity, acceleration,
temperature)
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Real Time Characteristics
Control Output
D/A
Plant
Amplification
Parallel I/O
Controller
Actuators/ sensors
Feedback
A/D
Demand
Conditioning
Parallel I/O
Computerised Control
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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

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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

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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
  activities
• Less obscure solutions, easier to validate
  correctness, easier analysis/design, easier
  testing, easier maintenance

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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

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Real Time Characteristics Software

• Example real-time requirements
• sample (at certain times) at a given sampling
  rate
• 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

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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

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Characteristics Interaction with hardware
Display
Sensors
keypad
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Characteristics Efficient Implementation

• efficiency of execution means that the programmer
  cannot always use the highest-level of
  representation
• 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
  microseconds

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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

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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.

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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

V
V
-
output
input

t
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Analogue components

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

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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.

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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

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Time analysis for a digital filter.
Sample/hold
D/A
Processor
A/D
output
Samplen1
Samplen
Process n instructions
t

• The higher the input bandwidth, the higher the
  sampling rate needs to be to collect sufficient
  samples
• the higher the sampling rate, the faster the
  processor has to be to execute the n instructions
  between samples

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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.

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Processing power required.

• Lets look at options for a DSP application

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Processing power and sampling rate...

• The faster the sampling rate the more power is
  required.
• 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
  applications

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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
  processing)
• 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.

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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

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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

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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
  chip!
• 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
  curve
• price of software tools ( compilers, debuggers,
  emulators, operating systems)

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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
  PROM (EPROM)
• 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

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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

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Embedded system components Peripherals

• interfaces for analogue peripheral devices

Input conditioning
Conversion/buffering
sensors
processing
Motors, actuators, pumps, temperature control,
position-control, audio, video etc
Output conditioning
Conversion/storage
digital
analogue
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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
Counter/timer
Power amplifier
A/D converter
Speed Sensor (tachometer) output
Parallel interface
microcontroller
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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
  implementation
• 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.

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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.

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Microcontrollers

• 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
  architectures
• there are also cheap 4-bit processors available
• usually a family of microcontrollers will have
  several variants with different or extra
  facilities added

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Microcontrollers

• Microcontroller will be available in several
  forms
• devices for prototyping
• programmer must be able to load code into the
  processor
• Ultra-Violet(UV) erasable EPROM or electrically
  erasable(EEPROM) parts are used to store the
  program
• 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
  this).

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Microcontrollers

• 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

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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..

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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.

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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
RAM
PROM
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Evolution..

• 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.

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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
  ready-to-go.
• 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)

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Board-based embedded systems

• VME-bus rack system

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Board-based embedded systems

• A VME-bus card.

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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)

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Embedded Microcontrollers are a big business

• World-Wide Microcontroller Shipments (in
  millions of dollars)
• '90 '91 '92 '93
  '94 '95 '96 '97 '98 '99
  '00
• 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
  Millions)
• '90 '91 '92 '93
  '94 '95 '96 '97 '98 '99
  '00
• 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

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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

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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
  applications.

78
Sales
79
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
  growing.
• 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.

80
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
  company).
• Do they support one-time programmable(OTP),
  windowed devices, mask-programmable(at the chip
  manufacturer) parts?

81
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
  released
• their life-cycle would naturally end here. They
  are no longer sold as standalone processors
  but..
• The basic design continues to be used when the
  processor core has been utilised as the heart of
  a highly integrated device.

82
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
  cycles
• 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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84
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.
85
Embedded processors - floor-plan - 68HC11
Here is a Motorola MC68HC11E9 microcontroller
chip. More RAM and ROM on-chip means more space
given to these.
86
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

89
Addressing memory...

• When 8-bit microprocessors appeared in the
  1970s, memory was ..
• expensive
• only available in small sizes (256 bytes up to
  1K)
• 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
  requirements
• memory started to become a limitation

90
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 !!!!!

91
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

92
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!
93

• 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)
  Controller
• 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
  Crystals
• Glue-less Interface to EPROM, SRAM, Flash EPROM,
  and EEPROM

94

• 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
  (HDLC/SDLC)
• Universal Asynchronous Receiver Transmitter
  (UART)
• 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
  Including
• 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

95
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
  cheaper)
• 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
  core.
• Buffering and low-level protocol management is
  performed by the specialised comms processor

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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.

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Space saving before..
Glue logic - probably a PLD
Address decoder
Chip select lines
RAM
Standard processor
ROM
Address Bus. The data bus and other connections
are not shown
and..
98
Space saving after..
Look..no glue logic required!
Chip select lines
RAM
Processor with built-in decoding for external
devices
ROM
Address Bus. The data bus and other connections
are not shown
99
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.

100
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
  technology.
• 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.

101
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.

102
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

103
DSP Background

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

104
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