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Embedded SystemsIntroduction


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Microprocessor bui ld ing blocks

1. ALU (Arithmetic Logic Unit): The ALU is a sequential logic circuitry that is

intended to perform arithmetic and logical

operations, such as ADD, SUBTRACT, AND, OR,

SHIFT.

Example of a primitive ALU (Input, Output, address

input or control input)

n-bit ALU and n-bit P

2. Registers: A register is a temporary (internal) storage element


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Microp rocessor bu i ld ing blocks (con td.)

3. BUSES:The registers and ALU are not permanently connected

together, but are joined by a DATA BUS. This bus allows

data to be passed from a register to the ALU at one instant

and from the ALU to a register at another instant.

The bus is, in fact, a parallel set of wires (conductive

silicon internal to a chip or tracks on a printed circuit

board), which carries information, and which connect all

elements together.

data bus, address bus andcontrol bus


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Microcontrol lers v s. Microp rocessors

Micro controllers are microcomputers on a chip. optimized to

control electronic devices.

Usually microcontrollers are used for controlling industrial

equipment and machinery and have therefore special

instructions as for example bit manipulation instructions.

What are the differences between a C and a P?

Nonvolatile Program and Data Memories Internal SRAM

A/D Analog Comparator

Internal Calibrated RC Oscillator Timers/Counters

External and Internal Interrupt Sources Sleep Modes

Serial Peripheral Interface (SPI), USART, Two-

wire Serial Interface

Watchdog


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Microcontrol lers and Embedded Systems

In control tasks the Cis usually embedded in thesystem. Embedded systems have minimalrequirements for memory and program size andneed to communicate with simple inputs andoutputs.

Keyboards, screens, disks, printers are seldomlyneeded by an embedded system.

Microcontrollers are usually dedicatedto one taskand run one specific program.


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High Level Languages (contd .)

High Level Low Level

1 One instruction = many machine

code instructions.

One instruction = one machine

code instruction.

2 Portable, task-oriented Machine specific, machine-oriented

3 More English-like Less easy to write and debug.


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Mach ines and app l iances that use C

Television, Satellite Receiver, Monitor, Modem, Router, Printer,Microwave oven, Sound System, Digital Camera, Car (most all of them),

Car stereo, Dishwasher, Dryer, Washing Machine, Ovens, Air Conditioner,

Cell phone, Digital Multi-Meter, Calculator, Medical Equipment (e.g. Heart

Monitors), Traffic Lights, Fax Machines, Copy Machine, Security

Systems, Fire Alarms, And MUCH more.

A typical mid range car has as many as 50 or more microcontrollers (e.g.in anti-lock brakes and in cruise control).


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Course Contents:

Introduction - Microcontrollers and Embedded Systems

Memories

I_O Ports

External Interrupts

Timers

Clock Options

Sleep Modes

Reset Sources

Reset and Interrupt Vectors

Watchdog Timer Communicating

Dealing with Analog Signals

+ CodeVision AVR: C-language Compiler

1- designing with uc’s_2011

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