Introduction to Microcontrollers

Introduction to Microcontrollers
25th February 2009 No Comments Uncategorised admin

Introduction

A microcontroller is a computer with most of the necessary support chips

onboard. All computers have several things in common, namely:

 

  •  A central processing unit (CPU) that ‘executes’ programs.
  •  Some random-access memory (RAM) where it can store data that is variable.
  •  Some read only memory (ROM) where programs to be executed can be stored.
  •  Input and output (I/O) devices that enable communication to be established

 

with the outside world i.e. connection to devices such as keyboard, mouse,

monitors and other peripherals.

There are a number of other common characteristics that define microcontrollers.

If a computer matches a majority of these characteristics, then it can be

classified as a ‘microcontroller’. Microcontrollers may be:

 

READ MORE…….

Introduction

A microcontroller is a computer with most of the necessary support chips

onboard. All computers have several things in common, namely:

 

  •  A central processing unit (CPU) that ‘executes’ programs.
  •  Some random-access memory (RAM) where it can store data that is variable.
  •  Some read only memory (ROM) where programs to be executed can be stored.
  •  Input and output (I/O) devices that enable communication to be established

 

with the outside world i.e. connection to devices such as keyboard, mouse,

monitors and other peripherals.

There are a number of other common characteristics that define microcontrollers.

If a computer matches a majority of these characteristics, then it can be

classified as a ‘microcontroller’. Microcontrollers may be:

 

  •  ‘Embedded’ inside some other device (often a consumer product) so that

 

they can control the features or actions of the product. Another name for a

microcontroller is therefore an ‘embedded controller’.

 

  • Dedicated to one task and run one specific program. The program is stored

 

in ROM and generally does not change.

 

  • A low-power device. A battery-operated microcontroller might consume as

 

little as 50 milliwatts.

 

A microcontroller may take an input from the device it is controlling and

controls the device by sending signals to different components in the device.

A microcontroller is often small and low cost. The components may be chosen

to minimise size and to be as inexpensive as possible.

The actual processor used to implement a microcontroller can vary widely. In

many products, such as microwave ovens, the demand on the CPU is fairly low

and price is an important consideration. In these cases, manufacturers turn to

dedicated microcontroller chips – devices that were originally designed to be

low-cost, small, low-power, embedded CPUs. The Motorola 6811 and Intel

8051 are both good examples of such chips.

A typical low-end microcontroller chip might have 1000 bytes of ROM and

20 bytes of RAM on the chip, along with eight I/O pins. In large quantities, the

cost of these chips can sometimes be just a few pence.

 Microcontroller types

The predominant family of microcontrollers are 8-bit types since this word

size has proved popular for the vast majority of tasks the devices have been

required to perform. The single byte word is regarded as sufficient for most

purposes and has the advantage of easily interfacing with the variety of IC

memories and logic circuitry currently available. The serial ASCII data is also

byte sized making data communications easily compatible with the microcontroller

devices. Because the type of application for the microcontroller may vary

enormously most manufacturers provide a family of devices, each member of

the family capable of fitting neatly into the manufacturer’s requirements. This

avoids the use of a common device for all applications where some elements of

the device would not be used; such a device would be complexan d hence

expensive. The microcontroller family would have a common instruction subset

but family members differ in the amount, and type, of memory, timer facility,

port options, etc. possessed, thus producing cost-effective devices suitable for

particular manufacturing requirements. Memory expansion is possible with offchip

RAM and/or ROM; for some family members there is no on-chip ROM,

or the ROM is either electrically programmable ROM (EPROM) or electrically

erasable PROM (EEPROM) known as flash EEPROM which allows for the

program to be erased and rewritten many times. Additional on-chip facilities

could include analogue-to-digital conversion (ADC), digital-to-analogue conversion

(DAC) and analogue comparators. Some family members include

versions with lower pin count for more basic applications to minimise costs.

 

Many microcontroller manufacturers are competing in the market place and

rather than attempting to list all types the authors have restricted the text to

devices manufactured by one maker. This does not preclude the book from

being useful for applications involing other manufacturer’s devices; there is a

commonality among devices from various sources, and descriptions within the

text can, in most cases, be applied generally. 

 

About The Author

Leave a reply

Your email address will not be published. Required fields are marked *

17 + five =