introduction of the 4 bit 4004 by Intel. A byproduct of Microprocessor development was Microcontroller. The same fabrication technology and programming concept that make the general purpose microprocessor also yielded the Microcontroller. Microprocessors A microprocessor is a general purpose digital computer central processing unit CPU . Although known as a Computer on Chip the Microprocessor in no sense a complete digital computer. Block diagram of a Microprocessor CPU which contains ALU Program counter PC , a stack 3
pointer SP ,some working registers , a clock timing circuit and interrupt circuit s is shown in the following figure Arithmetic and Logic Unit Accumulator Working Register
Fig.2.Block Diagram of a Microprocessor To make a computer microcomputer one must add memory usually RAM and ROM, memory decoders , an oscillator and a number of Input ,Output devices such as serial and parallel ports. In addition special purpose devices such as interrupt handler and counters may be added to relieve the CPU from time consuming counting or timing cores. When the Microcomputer is equipped with mass storage devices , I O peripherals such as a key board and a display CRT it yields a small computer that can be applied to a range of general purpose applications.
The hardware design of a microprocessor is arranged such that a very small or very large system can be configured around the CPU as the application demands as shown in Fig1. The prime use of the Microprocessor is to read data , perform extensive calculations on that data, and store those calculations in a mass storage device or display the results for human use. The programs used by microprocessor are stored in the mass storage device and loaded into RAM as user directs. A few microprocessor program are stored in ROM . The ROM based programs are primarily small fixed programs that operate peripherals and other fixed devices that are connected to the system. Microcontroller A Microcontroller is a programmable digital processor with necessary peripherals. Both microcontrollers and microprocessors are complex sequential digital circuits meant to carry out job according to the program instructions. Sometimes analog input output 4
interface makes a part of microcontroller circuit as mixed mode both analog and digital in nature.
A microcontroller can be compared to a Swiss knife with multiple functions incorporated in the same Integrated Circuits. Block diagram of a typical Microcontroller which is a true computer on a chip is shown below. The design incorporates all the features found in microprocessor CPU