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Embedded Computing System(06CS74)

UNIT - 1

Embedded systems
Processor embedded into a system
Embedded hardware units and devices in a system
Embedded software in a system
Examples of embedded systems
Embedded System-on-Chip (SoC) and use of VLSI circuit design technology
Complex systems design and processors; Design process in embedded system.
7 Hours

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Embedded Computing System(06CS74)

The definition of embedded system from the following
It is any device that includes a programmable computer but is not itself intended to be a general
purpose computer.‖

Embedded Systems are the electronic systems that contain a microprocessor or a
microcontroller, but we do not think of them as computers– the computer is hidden or embedded
in the system.‖

Differences between Harvard and Von Neuman architecture

1.It is Microcontroller based
2. It is for specific purpose
3. It is an embedded system
4. Power consumption is less
5. It is handye product

Von Neuman

It is Microprocessor based
It suits general purpose
It is a general system
Power consumption is more
Here enhancement possible

The Challenges faced in designing an embedded system
i>Amount and type of hardware needed
Optimizing the microprocessors, ASIPs and single purpose processors in the system
Optimizing according to the performance, power dissipation, cost and other design metrics the
system Optimizing hardware (memory RAM, ROM or internal and external flash or secondary
memory in the system, peripherals and devices internal and external to the system, ports and buses
in the system and power source or battery in the system).
ii> Taking into account the design metrics
Design metrics examples –power dissipation, physical size, number of gates and engineering,
prototype dissipation, physical size, number of gates and engineering, prototype development and
manufacturing costs.
iii> Optimizing the Power Dissipation
Clock Rate Reduction Operating Voltage Reduction Wait, Stop and Cache Disable Instructions
Clever real- time programming. It is by using of 'Wait' and 'Stop' instructions and disabling or
controlling certain units when not needed is one method of saving power during program
iv> Disable use of certain structural units of the processor to reduce power dissipation
Caches—when not necessary and Keep in disconnected state those structure units that are not
needed during a particular software-portion execution, for example display screen, timers or IO
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Embedded Computing System(06CS74)
units. Control of power requirement, for example, by screen auto-brightness control
v> Process Deadlines
Meeting the deadline of all processes in the system while keeping the memory, power dissipation,
processor clock rate and cost at minimum is a challenge
vi> Flexibility and Upgradeability
Ability to offer the different versions of a product for marketing and offering the product in
advanced versions later on.

Processor embedded into a system
i>Embedded general purpose processor
Fast context switching features, use of on-chip Compilers, for example, Intel® XScale™
Applications Personal Internet Client : Architecture-based PDAs, cell phones and other wireless
ii>Application Specific Instruction- Set Processor (ASIP
Microcontroller — Intel, Motorola, Hitachi, TI, Philips and ARM For example, an Intel® —
MCS51, Philips® Motorola — 68HC11, 68HC12, 68HC16
iii> Large Scale Embedded System 32-bit Microcontroller
ARM family Cortex-M3, Atmel ,AT91 series, ST10 series, Philips

Hitachi ,LPC 2000 series,

Texas Instrument SH7045F, C16x and TMS470R1B1M, Samsung S3C44B0X
iv> Application Specific Instruction-Set Processor (ASIP)
DSP or Texas Instruments- C28x Series, C54xx or C64xx or Analog Devices SHARC or
Media processor or TI DSP TMS320DM310 or Trimedia Phillips Media Processor 1x00
series for Processing Streaming and Data Networks and Image, Video and Speech: PNX 1300,
PNX 1500 (2002) IO processor or Network processor or A domain specific processor
v>GPP or ASIP core (s) GPP or ASIP core (s)
GPP or ASIP Integrated into either an Application Specific Integrated Circuit (ASIC), or a Very
Large Scale Integrated Circuit (VLSI) circuit or a FPGA core integrated with processor unit(s) in
a VLSI (ASIC) chip

Embedded hardware units and devices in a system
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Embedded Computing System(06CS74)

i)Processor : Program Flow and data path Control ,Unit (CU) —includes a fetch unit for fetching
instructions from the memory.Processor Execution Unit (EU) —includes circuits for arithmetic
and logical unit (ALU), and for instructions for a program control task, say, data transfer
instructions, halt, interrupt, or jump to another set of instructions or call to another routine or
sleep or reset
ii) Power Source
1. System own supply with separate supply rails for IOs, clock, basic processor and memory and
analog units, or
2. Supply from a system to which the embedded system interfaces, for example in a network
card, or
3. Charge pump concept used in a system of little power needs, for examples, in the mouse or
contact-less smart card.
iii) Clock Oscillator Circuit and Clocking
1. Appropriate clock oscillator circuit
2. Real Time Clock ( System Clock) and Timers driving hardware and software
iv) Reset Circuit
1. Reset on Power-up
2. External and Internal Reset circuit
3. Reset on Timeout of Watchdog timer
vi) Interrupts Handler

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Embedded Computing System(06CS74)
Interrupt Handling element for the external port interrupts, IO interrupts, timer and RTC
interrupts, software interrupts and exceptions
vii )IO Communication Unit a. Communication Driver(s) : Network Ethernet or serial driver
to communicate with host embedded system Expansion Facility … Serial Bus(es): For example,
UART (512 kbaud/s), 1-wire CAN (33 kbps), Industrial I C (100kbps), SM I C Bus 2
(100 kbps), SPI (100 kbps), Fault tolerant CAN (110 kbps), Serial Port (230 kbps), MicroWire
(300 kbps), … Parallel Bus(es): PCI, PCI-X

Embedded software in a system
ROM Image

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Embedded Computing System(06CS74)

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Embedded Computing System(06CS74)

Embedded System-on-Chip (SoC) and use of VLSI circuit design technology

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Embedded Computing System(06CS74)

Design process in embedded system
Each problem component first abstracted. For example, Display picture and text as an abstract
class Robotic system problem abstraction in terms of control of motors in different degrees of
freedoms. Application software abstracted as concurrently running multiple threads and interrupt
service threads.
Program Model
Procedure Oriented , Objected Oriented , Sequential processes, Concurrent processes , State
Object oriented Model Object oriented Model:- Classes , Objects , Interfaces, Package
Hardware and Software architecture
Assumed to consists multiple layers , Each architectural layer be well understood before a design
Extra functional Properties Extra functional Properties
Extra functionalities required in the system being developed be well understood from the design.
System Related Family designs
Families of related systems developed earlier taken into consideration during designing
Modular Design
Decomposition of software into modules that are to be implemented. Modules should be such
that they can be composed (coupled or integrated) later. Effective Modular design should ensure
effective (i) function independence, (ii) cohesion and (iii) coupling.
Modules: Be clearly understood and maintain continuity. Appropriate protection strategies are
necessary for each module. A module is not permitted to change or modify another module
functionality. For example, protection from a device driver modifying the configuration of
another device
Mapping : Mapping into various representations done considering the software requirements.
For example, data flow in the same path during the program flow can be mapped together as a
single entity.

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Embedded Computing System(06CS74)
Transform and transaction mapping Transform and transaction mapping For example, an
image is input data to a system; it can have a different number of pixels and colors of each pixel.
The system has to store or process each pixel and color Transform mapping of image is done by
appropriate compression and storage algorithms. Transaction mapping is done to define the
sequence of the images

Processors in Embedded system

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