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Basic Concepts of Microprocessors
Differences between:
– Microcomputer – a computer with a
microprocessor as its CPU. Includes memory, I/O
etc.
– Microprocessor – silicon chip which includes
ALU, register circuits & control circuits
– Microcontroller – silicon chip which includes
microprocessor, memory & I/O in a single
package.
What is a Microprocessor?
• The word comes from the combination micro and
processor.
– Processor means a device that processes whatever. In
this context processor means a device that processes
numbers, specifically binary numbers, 0’s and 1’s.
• To process means to manipulate. It is a general term that
describes all manipulation. Again in this content, it means to
perform certain operations on the numbers that depend on the
microprocessor’s design.
What about micro?
• Micro is a new addition.
– In the late 1960’s, processors were built using discrete
elements.
• These devices performed the required operation, but were too
large and too slow.
– In the early 1970’s the microchip was invented. All of
the components that made up the processor were now
placed on a single piece of silicon. The size became
several thousand times smaller and the speed became
several hundred times faster. The “Micro”Processor
was born.
Was there ever a “mini”-
processor?
• No.
– It went directly from discrete elements to a
single chip. However, comparing today’s
microprocessors to the ones built in the early
1970’s you find an extreme increase in the
amount of integration.
• So, What is a microprocessor?
Definition of the Microprocessor
The microprocessor is a programmable device
that takes in numbers, performs on them
arithmetic or logical operations according to
the program stored in memory and then
produces other numbers as a result.
Definition (Contd.)
• Lets expand each of the underlined words:
– Programmable device: The microprocessor can perform
different sets of operations on the data it receives depending
on the sequence of instructions supplied in the given
program.
By changing the program, the microprocessor manipulates
the data in different ways.
– Instructions: Each microprocessor is designed to execute a
specific group of operations. This group of operations is
called an instruction set. This instruction set defines what the
microprocessor can and cannot do.
come from somewhere.
• It comes from what is called “input devices”.
• These are devices that bring data into the system
from the outside world.
• These represent devices such as a keyboard, a
mouse, switches, and the like.
Definition (Contd.)
– Numbers: The microprocessor has a very narrow view on life. It
only understands binary numbers.
A binary digit is called a bit (which comes from binary digit).
The microprocessor recognizes and processes a group of bits
together. This group of bits is called a “word”.
The number of bits in a Microprocessor’s word, is a measure of its
“abilities
Words, Bytes, etc.
• The earliest microprocessor (the Intel 8088 and Motorola’s
6800) recognized 8-bit words.
– They processed information 8-bits at a time. That’s why they are
called “8-bit processors”. They can handle large numbers, but in
order to process these numbers, they broke them into 8-bit pieces
and processed each group of 8-bits separately.
• Later microprocessors (8086 and 68000) were designed with
16-bit words.
– A group of 8-bits were referred to as a “half-word” or “byte”.
– A group of 4 bits is called a “nibble”.
– Also, 32 bit groups were given the name “long word”.
• Today, all processors manipulate at least 32 bits at a time and
there exists microprocessors that can process 64, 80, 128 bits
Arithmetic and Logic Operations:
• Every microprocessor has arithmetic operations such as add
and subtract as part of its instruction set.
– Most microprocessors will have operations such as multiply and
divide.
– Some of the newer ones will have complex operations such as
square root.
• In addition, microprocessors have logic operations as well.
Such as AND, OR, XOR, shift left, shift right, etc.
• Again, the number and types of operations define the
microprocessor’s instruction set and depends on the specific
microprocessor.