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The 8051 Microcontrollers &

Embedded Systems

CHAPTER-1

The 8051 MicrocontrollersPrepared By: Rutul Patel (EEE Dept.)

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Outline

What is Microcontroller?

Microcontroller VS Microprocessor

Microcontrollers for embedded systems

Some Embedded Products

Criteria For Choosing A Microcontroller

Key features of 8051

Types of ROM

Types of RAM

8051 block diagram Different versions of 8051

Different 8051 chips

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What is Microcontroller?

Heart = Microprocessor

Blood = Data

Artery = Output (purified blood)

Vein = Input (unpurified blood)

Heart beat = Clock frequency (Timer)

Combination of all this parts + Memory = Microcontroller

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Microcontroller VS Microprocessor

Parameter Microprocessor Microcontroller

RAM, ROM No Yes

I/O ports No Yes

Timer & serial COM port No Yes

Versatility Yes No

Clock speed In terms of GHz In terms of MHz

Use General purpose Application specific

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Microcontrollers for embedded

systems

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Some Embedded Products

Home appliances

Air conditioners, microwaves etc.

Security systems

Camcorder

Fax machine

Printers

Air bag Engine control

ATM

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Criteria For Choosing A

Microcontroller

1st criterion

Speed : highest speed supported

Packaging : DIP or QFP

Power consumption

Amount of RAM & ROM on the chip

No. of I/O pins & the timers on the chip

Up gradation facility

Cost per unit

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Contd

2nd Criterion

Ease of developing products

Availability of an assembler, debugger, a codeefficient C-compiler, emulator, simulator &

technical support

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Contd

Wide availability and reliable sources of theMicrocontroller

The 8051 family has the largest number of

diversified (multiple source) suppliers Intel (original)

Atmel

Philips/Signetics

AMD Infineon (formerly Siemens)

Dallas Semiconductor/Maxim

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Key Features Of 8051

The 8051 is an 8-bitprocessor

The CPU can work on only 8 bits of data at a time

The 8051 has

16-bit address bus & 8-bit data bus

128 bytes of RAM

4K bytes of on-chip ROM ( max. 64K bytes achieved)

Two timers

One serial port

Four I/O ports (each 8 bits wide)

6 interrupt sources

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Types Of ROM

Mask Programmed ROM (MROM) : Programmed at the factory.

Programmable ROM (PROM) : Can be custom-programmed by the user (once) using

special circuitry.

Erasable Programmable ROM (EPROM) : Can also be programmed and erased by the user using

ultraviolet light and special circuitry external to thecomputer.

Electrically Erasable PROM (EEPROM) : Can be erased and reprogrammed by special circuitry

within the computer.

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Types Of RAM

SRAM stores binary bits in such a manner that the

bits remain in RAM as long as power to thechip is not interrupted

Requires 6 transistor to store a bit So its a large size & lower speed memory

DRAM

requires that stored data be refreshed, orrewritten, periodically

Requires 1 transistor & a capacitor to storea bit

So its a small size & higher speed memory

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8051 Block Diagram

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Different Versions Of 8051

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Different 8051 chips

8751 microcontroller UV-EPROM

PROM burner

UV-EPROM eraser takes 20 min to erase

AT89C51 from Atmel Corporation Flash (erase before write)

ROM burner that supports flash

A separate eraser is not needed

DS89C4x0 from Dallas Semiconductor, now part of

Maxim Corp. Flash

Comes with on-chip loader, loading program to on-chip flash via PCCOM port