1. INTRODUCTION TO MICROPROCESSOR AND MICROCOMPUTER
A microprocessor is a programmable electronics chip that has computing and decision
making capabilities similar to central processing unit of a computer. Any microprocessorbased systems having limited number of resources are called microcomputers. Nowadays,
microprocessor can be seen in almost all types of electronics devices like mobile phones,
printers, washing machines etc. Microprocessors are also used in advanced applications like
radars, satellites and flights. Due to the rapid advancements in electronic industry and large
scale integration of devices results in a significant cost reduction and increase application of
microprocessors and their derivatives.
Fig.1 Microprocessor-based system
Bit: A bit is a single binary digit.
Word: A word refers to the basic data size or bit size that can be processed by the
arithmetic and logic unit of the processor. A 16-bit binary number is called a word in
a 16-bit processor.
Bus: A bus is a group of wires/lines that carry similar information.
System Bus: The system bus is a group of wires/lines used for communication
between the microprocessor and peripherals.
Memory Word: The number of bits that can be stored in a register or memory
element is called a memory word.
Address Bus: It carries the address, which is a unique binary pattern used to identify
a memory location or an I/O port. For example, an eight bit address bus has eight
lines and thus it can address 28 = 256 different locations. The locations in
hexadecimal format can be written as 00H – FFH.
Data Bus: The data bus is used to transfer data between memory and processor or
between I/O device and processor. For example, an 8-bit processor will generally
have an 8-bit data bus and a 16-bit processor will have 16-bit data bus.
Control Bus: The control bus carry control signals, which consists of signals for
selection of memory or I/O device from the given address, direction of data transfer
and synchronization of data transfer in case of slow devices.