Introduction to Microprocessor: Microprocessor is an electronic chip that functions as the central
processing unit (CPU) of a computer. The microprocessor based systems with limited resources are
called as microcomputers. Now-a-days microprocessors are found in almost all electronic machines
and appliances in its different form. Some common devices using microprocessors are computer,
printers, automobiles, washing machines, microwave ovens, mobile phones, fax machines, Xerox
machines and advanced instruments like radar, satellites, flights etc.
Almost all microprocessors use the basic concept of “stored program execution”. By this concept,
programs are stored sequentially in memory locations. The microprocessor will fetch the instructions
one after the other and execute them in its arithmetic and logic unit. So it is necessary for the user
to know about the internal resources and features of the microprocessor. The programmers must
also understand the instructions that a microprocessor can support. Every microprocessor will have
its own associated set of instructions and this list is given by all the microprocessor manufacturers.
Programs are written using mnemonics called the assembly level language and then they are
converted into binary machine level language. This conversion can be done manually or using an
application called assembler.
In general, the programs are written by the user for a microprocessor to work with real world data.
These data are available in many forms and are from many sources. A microprocessor based system
need a set of memory units, set of interfacing circuits for inputs and a set of interfacing circuits for
outputs. All circuits put together along with microprocessor are called as microcomputer system.
The physical components of the microcomputer system are in general called as hardware. The
program which makes this hardware useful is called as software.
Origin of Microprocessor
The breakthrough in transistor technology led to the introduction of minicomputers of the 1960s
and the personal computer revolution of the 1970s.Microprocessors evolution is categorized into
five generations i.e.first, second, third, fourth, and fifth generations.
First Generation (1971-73)
The microprocessors that were introduced in 1971 to 1972 were referred to as the first generation
systems. Intel Corporation introduced 4-bit 4004 at 108 kHz, the first microprocessor in 1971, codeveloped by Busicom, a Japanese manufacturer of calculators. In 1972, Intel made the 8-bit 8008
and 8080 microprocessors.
Second Generation (1974-78)
The second generation marked the beginning of very efficient 8-bit microprocessors. Some of the
popular processors are Motorola’s 6800 and 6809 and Intel’s 8085, Zilog’s Z80. The distinction
between the first and second generation devices is primarily the use of newer semiconductor
technology to fabricate the chips. They were manufactured using NMOS technology.
Third Generation (1979-80)