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 ABC of Electronics
The 8051 microcontroller

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Introduction

The 8051 microcontroller was introduced by Intel in 1981 as the successor to its already successful 8048 microcontroller, used in the original IBM PC keyboard, for example. The new, so-called MCS-51 architecture comprised 128 bytes of RAM ("Random Access Memory"), 4Kb of ROM ("Read Only Memory"), two timers or counters, a serial port and four parallel I/O ("Input/Output") ports on a single chip. The 8051 microcontroller has an 8-bit data bus, meaning that the CPU ("Central Processing Unit") is capable of handling just 8 bits of data at any one time, so larger data must be divided in 8-bit blocks for processing. It is, however, capable of addressing 64K of program memory and 64K of data memory separately.

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8051 Microcontroller Features, Applications, etc.

The 8051 microcontroller architecture is one of the most popular in the world and is most commonly found in control, instrumentation and embedded systems applications using assembly language. Programming the 8051 microcontroller is achieved by placing control words into various so-called SFRs ("Special Function Registers"), which are the control and data registers for on-chip facilities and also include the PSW ("Program Status Word"), containing CPU flags. The 8051 microcontroller instruction set is easy to understand and development tools for the family are widely available, so starting to develop an application is straightforward and inexpensive.

The 8051 microcontroller is similar to the ROM-less 8031, also originally introduced by Intel and its competitors include PIC microcontrollers, which are available in several different types, including those which, unlike the 8051 microcontroller, have analogue-to-digital converters built in. PIC processors are popular because of their low cost and wide availability and similar comments apply to the ARM 32-bit RISC ISA architecture, which is suitable for low power applications and has become dominant for microcontrollers in consumer electronics, including mobile phones, digital media players, etc..

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Microcontrollers are available in numerous architectures from numerous vendors, however and it is sometimes surprising to learn how many everyday systems use a microcontroller as their main control unit. In fact, microcontrollers are embedded in almost any device that operates from mains or battery power and there may be anything up to 50 such devices in the average household.

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A standard DVD player, for example, contains a microcontroller that performs control panel management, video and audio processing, etc. and numerous other devices and systems, such as TV remote controls, satellite TV receivers, ABS braking systems and even toasters rely on a microcontroller for their operation.

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