Embedded Systems

MCLR: First pin of PIC 18F4520

MCLR - Master Clear (It is an active low pin)

MCLRE - Master Clear Enable

MCLRE = ON  (It means Enable the reset function)

MCLRE = OFF (It means Disable the reset function)

TRIS is one of the register in PIC Microcontroller.

PIC 18F4520 has 5 ports such as PORTA, PORTB, PORTC, PORTD & PORTE

For example TRISA = 0; It indicates all pins of PORTA act as OUTPUT

                  TRISA = 1; It indicates all pins of PORTA act as INPUT

The term “Micro computer” usually conjures up in the minds of many people starting from the image of a PC to a laptop or any application specific system. On the other hand an embedded system has always been in the focus to design such system which is more custom driven and remains invisible to the users. It is a single chip controller used in more than 90% of all the world’s computer equipments. 

Today's automobiles contain many such embedded processors, controlling various tasks in real time tasks as antilock braking, climate control, engine control, audio system control, airbag deployment etc. These embedded systems are networked and often use simple executives (OS kernels) or real-time operating systems with typically small footprints, support for real-time scheduling without any hard drives. Many embedded systems also interact with their physical environment using a variety of sensors and/or actuators.

The lesson will more concetrate on design of such novel application specific system with reference to battery powered electric car. In order to manage this constrained resource for driving such system we hav eto design an energy efficient scheduling process. This needs a novel algorithm design using Machine learning.

TOPICS TO BE DISCUSSED

• System
• Embedded System
• Components
• Classifications
• Processors
• Other Hardware
• Software

INTRODUCTION:

What is a system?,

  A system is a way of working, organizing or doing one or many tasks according to a fixed plan, program or set of rules.

  A system is also an arrangement in which all its units assemble and work together according to the plan or program.

SYSTEM EXAMPLES

WATCH

It is a time display SYSTEM

Parts: Hardware, Needles, Battery, Dial,

           Chassis and Strap

Rules

1.All needles move clockwise only

2.A thin needle rotates every second

3.A long needle rotates every minute  

4.A short needle rotates every hour

5.All needles return to the  original position after 12 hours

WASHING MACHINE

It is an automatic clothes washing SYSTEM

Parts: Status display panel, Switches & Dials, Motor, Power supply & control unit, Inner water level sensor and solenoid valve.

Rules

1.Wash by spinning

2. Rinse

3. Drying

4.Wash over by blinking

5. Each step display the process stage

6. In case interruption, execute only the remaining.

EMBEDDED SYSTEM DEF

Definition: An Embedded System is one that has computer hardware with software embedded in it as one of its important components.     

Its software embeds in ROM (Read Only Memory). It does not need secondary memories as in a computer.

Components of computer hardware:

A Microprocessor

A Large Memory (Primary and Secondary) (RAM, ROM and caches)

Input Units (Keyboard, Mouse, Scanner, etc.)

Output Units (Monitor, printer, etc.)

Networking Units (Ethernet Card, Drivers, etc.)

I/O Units (Modem, Fax or Modem, etc.)

COMPONENTS OF EMBEDDED SYSTEM:

1). It has Hardware:

  Processor, Timers, Interrupt controller, I/O Devices, Memories, Ports, etc.

2). It has main Application Software:

  Which may perform concurrently the series of tasks or multiple tasks.

3). It has Real Time Operating System (RTOS):

  RTOS defines the way the system work. Which supervise the application software. It sets the rules during the execution of the application program. A small scale embedded system may not need an RTOS.

EMBEDDED SYSTEM CONSTRAINTS

An embedded system is software designed to keep in view three constraints:

1. Available system memory

2. Available processor speed –The need to limit the power dissipation

  When running the system continuously in cycles of wait for events, run, stop and wakeup.

 What makes embedded systems different?

• Real-time operation
• size
• cost
• time
• reliability
• safety
• energy
• security.

VARIOUS PROCESSOR:

1. General Purpose processor (GPP):

  Microprocessor,   Microcontroller,  Embedded Processor,   Digital signal Processor

2. Application Specific System Processor (ASSP)

3. Multi Processor System using GPPs.

EMBEDDED PROCESSOR:

• Special microprocessors & microcontrollers often called, Embedded processors.
• An embedded processor is used when fast processing fast context-switching & atomic ALU operations are needed.

Examples : ARM 7, INTEL i960, AMD 29050.

APPLICATION SPECIFIC SYSTEM PROCESSOR (ASSP):

• ASSP is dedicated to specific tasks and provides a faster solution.
• An ASSP is used as an additional processing unit for running the application in place of using embedded software.

Examples : IIM7100, W3100A.

MULTI PROCESSOR SYSTEM USING GPPs:

• Multiple processors are used when a single processor does not meet the needs of different task.
• The operations of all the processors are synchronized to obtain an optimum performance.

APPLICATIONS:

• Household appliances:   Microwave ovens, Television, DVD   Players & Recorders

• Audio players
• Integrated systems in aircrafts and missiles

• Cellular telephones
• Electric and Electronic Motor controllers
• Engine controllers in automobiles
• Calculators
• Medical equipments
• Videogames
• Digital musical instruments, etc.