Classification of Embedded Systems

Three Types of Embedded Systems are :

(1) Small Scale (2) Medium Scale(3) Sophisticated

Small Scale Embedded Systems

Designed with a single 8 or 16 bit µC. Little Hardware & Software

complexities. Involves Board level design. May be Battery Operated. Programming Tools Needed:

Editor, Assembler, Cross Assembler specific to µC or µP used.

Medium Scale Embedded Systems

Designed with Single or a few 16-32 Bit µC or DSP or RISC Computer,

Hardware & Software Complexities Programming Tools: RTOS, Source Code

Engg. Tools, Simulator, Debugger, IDE. May employ readily available ASSP and

IP for various functions*

Sophisticated Embedded Systems

Have enormous H/W and S/W complexities, may need scalable or configurable processors and PLA

Used for cutting edge application that needs H/W & S/W Co-design and integration in final system

Constrained by processing speed available in their Hardware

Certain S/W functions implemented in H/W* to obtain additional speed by saving execution time.

Development Tools for such systems may not be readily available at a reasonable cost or may not be available at all

Processor Types Used in New Embedded Designs

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

4-bit 8-bit 16-bit 32-bit 64-bit Special

1998-19991999-2000

Selection of a Processor

Instruction Set, Pipelining, Super Scalar Execution.

Data Bus Width (8-16-32 Bits) for Arithmetic. Floating Point Coprocessor, Cache Memory On-chip peripheral devices, Clock Frequency, Availability of Retarget-able Compiler and

Hardware Software Co-design Tools Power Saving Modes available Cost [Components, Development tools, NRE]

Types of Processors used in Emb. Systems

General Purpose Processor (GPP): Microprocessor Micro-controller Digital Signal Processor Embedded Processor

Application Specific System Processor (ASSP)

Multiprocessor Systems using GPP Application Specific Instruction Processor

(ASIP)

Microprocessor (µP):

Single VLSI Chip having CPU and (may have) Cache memory, Floating point Arithmetic Coprocessor, Pipelining Architecture to process instructions faster.

CPU Instruction Set supports ALU operations, Data Transfer and Stack operations, Input and Output, Program Control, Sequencing and Supervisory operations

Software located in external memory Chips

Examples- Microprocessors

Intel 8085Intel 8086/ 88

8 Bit 16 bit

Simple control Applications

Intel 80386Intel 80486

32 bit Graphics Accelerator, Network Interface card

Pentium 64 bit Encryption Engine with 0.464 Gbps data rate

PowerPC MPC 823

32 Bit Floating Pt Coprocessor, USB, IrDA,

Microcontrollers

Contains ROM, RAM Memories on Chip Enhanced Input Output capabilities Limited Computational Abilities More Functional Units on Chip:

Timers, Watchdog Timer, Interrupt Controller, UART, Parallel I/O Ports, A/D Converter and PWM Circuit for D/A converters

Functional Circuits in a Chip or Core of Microcontroller

Processor ROM/ EPROM I/O Ports Controls and Interfaces

Data and

Stack RAM

Timers

External MemoryInterface

Serial UART

A/D Converter

Interrupt Controller

PWM for D/A

WatchdogTimer

Microcontroller Examples

68HC11, HC12

Motorola CISC

8051, 80251 Intel CISC

80186, 80386

Intel CISC

PIC 16F84, PIC 16F876

Microchip CISC

Enhancement of ARM7, ARM9

TI CISC with RISC

Embedded Processor

Specially designed µC / µP with:(1) Fast Context Switching and thus lower latencies of

the task in complex real time applications

(2) Atomic ALU Operations and thus no shared data problem

(3) RISC Core for fast, more precise and intensive calculations by embedded software

Needed in Real time Image processing and Aerodynamics Applications

Examples- Embedded Processors

ARM 7 and ARM 9

Image Processing

Intel i960 4 Channel DMA Controller

Digital Signal Processor

Computational capabilities of a µP Has Multiply – Accumulate (MAC) Units Very Large Instruction Word Processes Single Instruction Multiple

Data(SIMD) Fast processing of Discrete Cosine

Transforms and Inverse (IDCT) algorithms in Image Processing, Multimedia, Audio, Video, HDTV, DSP Modems and Telecom Processing Systems

Examples - DSP

TMS 320C6211 Texas Instruments

SHARC Analog Devices

5600xx Motorola

Application Specific System Processor (ASSP)

Dedicated to perform specific tasks in H/W Like

Provides Faster Solution using a single Chip Configured & Interfaced with the rest of ES.

Target Application Examples: Video Compression & Decompression (MPEG) Encryption and Decryption Implementations Serial to Ethernet Converter Application

Compression & Decompression Application

in MPEG2 or MPEG4 Standards Compression of Video signal is done before

storing or transmitting. Decompression is done before retrieving or receiving these signals

If embedded Software is run on GPP, separate DSP(s) are required to achieve real time processing. A single dedicated ASSP processor provides a faster solution.

Encryption & Decryption Applications

When 2 Systems needs data communications on a common bus and protocol, Embedded Software (with some RTOS feature) may take longer time than a hardware based approach

ASSP Processor (W3100) from i2Chip has, for example TCP, UDP, IP, ARP, Ethernet 10/100 Media Access Control (MAC)

Provides RTOS less, Internet Connectivity in H/W 5 times faster than a GPP based software solution

Serial to Ethernet Converter Application

IIM 7100 processes data in Real Time by hardware protocol stack

Requires no change in Application Firmware

Provides economical and smallest RTOS solution.

Multiple Processor System using GPP Multiple GPP are used in Mobile

Phone. Tasks performed are: Speech signal compression and coding Dialing Modulating & transmitting Demodulating and Receiving Signal decoding and Decompression interface to LCD display and Keypad SMS protocol based messaging and

displays

Multiple Processors in Video Conferencing

Image Pixels are just 144 x 176 as against 525 x 625 pixel in video picture on TV.

30 Samples of Images have to be taken in a second

144 x 176 x 30 = 760320 Pixels per second are to be processed by Compression before transmission

A single DSP does not suffice. Multiple DSP(s) are needed to process images during Video Conferencing in real time.

Application Specific Instruction Processor-ASIP

For many Applications, the GPP cores may not suffice. For examples: Security Applications, Smart Cards, Video games, Palmtop computers, Cell phones, Mobile Internet, Satellite Missile Systems Gbps Transceivers and Gbps LAN

systems

Application Specific Instruction Processor-ASIP

‘Special Processing Units’ needed in a VLSI designed Circuit to function as a Processor, called Application Specific Instruction Processors (ASIP)

Both the Configurable processor (FPGA cum ASIP) and Non-configurable processors (DSP, µP or µC) might be needed on a chip.

Examples: (1) Cell phone (2) ASIP for HDTV to process an image with 1920 x 1020 pixels on TV screen.