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The 8051 Microcontroller

and Embedded Systems

Chapter 1

The 8051 Microcontroller

From the text by Mazidi & Mazidi (2000)

Presentation developed by Martin Hebel

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Microcontrollers & Embedded Processors

Microprocessors, such as Intel Pentium and

Motorola 68000 contain no appreciableRAM or ROM and are referred to as general

purpose microprocessors. External devices

must be connected to make them functionaland useful.

Microcontrollers contain in-chip RAM,

ROM and other peripherals making themideal for small, inexpensive applications.

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Unlike in computer systems, the program in

microcontrollers is stored in non-volatileROM. RAM is used for variables, registers

and other temporary information.

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Embedded Systems

Embedded products use a microcontroller to

perform specific tasks, such as a printer toaccept the data and print it.

See Table 1-1 for many more products.

A general-purpose CPU may also be used

where high speed and very complex

operations or I/O is required.

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Choosing a uC

Major Families (but not all inclusive):

Motorola 68HC11

Intel 8051 (MCS51 family)

Zilog Z8

Microchip PICs (PIC16, PIC17,PIC18)Atmel AVRs

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Basis for choosing:

Meeting computing needs and cost effectiveness. Speed

Packaging

Power consumption

On-chip RAM/ROM

Number of I/O pins

Ability to upgrade

Cost per unit

On-chip peripherals/features

Availability/cost of software development tools such as

compilers, assemblers, debuggers.

Availability of resources, forums, books, on-line

information (such as www.8052.com).

http://www.8052.com/http://www.8052.com/

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Software/Hardware

AssemblersSpecific packages for converting

Assembly code to a controllers native binarycode.

CompilersConvert high level code to

Assembly/native binary (free to $1000+)

SimulatorsPC based simulation for

testing/debugging code (free to $1000+)

EmulatorsHardware which interfaces with PC

software to monitor in real time the emulatedcontroller ($100 to

$1000+) for debugging.

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Overview of the 8051

Intel introduced it in 1981, one of the first

microcontrollers. Of 8-bit controllers, the 8051 has the largest

base of suppliers.

Has four I/O ports, each 8-bit wide.

Became very popular when Intel began

leasing out the core to other companies. All

derivatives must be backwards compatible. Original member of the MCS 51 family.

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8051 Features

4K ROM Internal, up to 64K external

128 Bytes User RAM Internal, up to 64Kexternal (addressing shared with ROM)

2 Timers

32 I/O pins

1 Serial Port

6 Interrupt Sources

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Various 8051 Controllers

OTP Versions (One-Time-Programmable)

UV Erasable EPROM EEPROM

NV-RAM

FLASHOriginal 8051 ran at 12 MHz, and required 12

clock cycles to perform a single instruction

cycle (effectively 1 Million Instructions perSecond (MIPs)

Today's 8051 run up at 30 to 50MHz andperform a instruction each clock cycle.

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