8051: Intel Microcontroller

Topics: Central processing unit, Addressing mode, Interrupt Pages: 38 (8949 words) Published: February 24, 2013
Dr. Y. Narasimha Murthy.Ph.D


Introduction :

A decade back the process and control operations were totally implemented by the Microprocessors only. But now a days the situation is totally changed and it is occupied by the new devices called Microcontroller. The development is so drastic that we can’t find any electronic gadget without the use of a microcontroller. This microcontroller changed the embedded system design so simple and advanced that the embedded market has become one of the most sought after for not only entrepreneurs but for design engineers also.

What is a Microcontroller?

A single chip computer or A CPU with all the peripherals like RAM, ROM, I/O Ports, Timers , ADCs etc... on the same chip. For ex: Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X etc… MICROPROCESSORS & MICROCONTROLLERS:


A CPU built into a single VLSI chip is called a microprocessor. It is a general-purpose device and additional external circuitry is added to make it a microcomputer. The microprocessor contains arithmetic and logic unit (ALU), Instruction decoder and control unit, Instruction register, Program counter (PC), clock circuit (internal or external), reset circuit (internal or external) and registers. But the microprocessor has no on chip I/O Ports, Timers , Memory etc.

For example, Intel 8085 is an 8-bit microprocessor and Intel 8086/8088 a 16-bit microprocessor. The block diagram of the Microprocessor is shown in Fig.1


Fig.1 Block diagram of a Microprocessor.


A microcontroller is a highly integrated single chip, which consists of on chip CPU (Central Processing Unit), RAM (Random Access Memory), EPROM/PROM/ROM (Erasable Programmable Read Only Memory), I/O (input/output) – serial and parallel, timers, interrupt controller. For example, Intel 8051 is 8-bit microcontroller and Intel 8096 is 16-bit microcontroller. The block diagram of Microcontroller is shown in Fig.2.


Fig.2.Block Diagram of a Microcontroller

Distinguish between Microprocessor and Microcontroller

|S.No |Microprocessor |Microcontroller | |1 |A microprocessor is a general purpose device which is |A microcontroller is a dedicated chip which is also called single| | |called a CPU |chip computer. | |2 |A microprocessor do not contain on chip I/o Ports, |A microcontroller includes RAM, ROM, serial and parallel | | |Timers, Memories etc.. |interface, timers, interrupt | | | |circuitry (in addition to CPU) in a single chip. | |3 |Microprocessors are most commonly used as the CPU in |Microcontrollers are used in small, minimum component designs | | |microcomputer systems |performing control-oriented applications. | |4 |Microprocessor instructions are mainly nibble or byte |Microcontroller instructions are both bit addressable as well as | | |addressable |byte addressable. | |5 |Microprocessor instruction sets are mainly intended |Microcontrollers have instruction sets catering to the control of| | |for catering to large volumes of data. |inputs and outputs. | |6...
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