REGISTERS AND MICRO OPERTIONS

By Simran Bansal (13BTCSNR008)simransinghbansal.blogspot.com

Unit - I

INDUS INTERNATIONAL UNIVERSITYV.P.O. Bathu, Tehsil Haroli, Distt. Una, Himachal Pradesh-174301, India.Tel:9318797101/2/3

E-Mail:Info@iiuedu.in Website:www.iiuedu.in

Book Refered: Computer System Architecture By M. Morris Mano

Sept 16, 2014

Basic Terms• Nibble: Nibble is the group of 4 bits.• 1 Byte: 1 Byte is the group of 8 bits.• Logic Gates: These gates are use to perform logical

operations based on zero and one.• Flip flops: The flip-flop is the basic unit of digital memory. A

flip-flop can remember one bit of data. Sets of flip-flops are called registers, and can hold bytes of data. Sets of registers are called memories, and can hold many thousands of bits, or more.

• Registers: Registers are the small portion of memory available in digital processor and made up with the combination of flip flops. Generally in a C.P.U we have 8, 16, 32, 64 bit registers are available.

Some Basic Terminologies

• Micro operations: These are those operations which are perform on the data execute on the register.

e.g: Shift, Clear, Load, Count.• Register Transfer Language: The

notations which are used in the representation of micro operations are known as Register Transfer Language (RTL).

Register Types

Registers are generally designed by capital letters.e.g:• MAR(Memory address Register)• PC(Programming Counter)• IR(Instruction Register)

Register transfer

Register transfer is the process of transfer of information from one register to another. The register transfer can be done with the help of control function.

Basic symbols for Register Transfers

Symbols Description Examples

Letters or Numbers Donates a Register MAR, R1, R2

Parenthesis Donates a part of Register

R2(0-7), R2(L)

Arrow ← Donates a transforms of information

R2←R1

Comma , Separates two micro operations

R2←R1, R1←R2

Bus and memory transfer

Three – State Bus Buffers

The three state gates are also enable us to construct a BUS instead of Multiplexer.These gates can perform any conventional logic.ThreeStateBufferGate:

Paractical Approch to 3 – State Buffer Bus

In the Image:We have take the 3 – State buffer bus line or data bus line.If any of component is inactive the all bus will be in Hi-z or High impedance state.

Memory transfer operations

Process of memory word to communicate to the outside environment is called memory read operation and vice versa is called memory write operation.e.g. Read: DR←M[AR]II’y in case of write:

Write: M[MR]←DR

TYPES OF MICROOPERATIONS

Arithmetic Micro operations

These micro operations are used to perform arithmetic logics with the help of logic circuits.The RTL can be represent as:

Logical Micro operations

These are used to perform Logical Micro operations:The RTL can be represent as shown on right side.

Shift Micro operations

These are used for serial transfer of data and of following type:

Athematic, Logic and Shift Unit

ALU is the combination of Athematic, Logic and Shift Unit.

Block diagram of CPU