REGISTER TRANSFER&

MICROOPERATIONS

By Sohaib

Digital System Overview

Each module is built from digital components Registers Decoders Arithmetic elements Control logic

Collection of modules is a digital system.

Modules connected by common data and control paths.

Microoperations

Elementary operation performed on data within one or more registers

Operation result could update same register or another register

Examples: shift, count, clear, and load Bidirectional shift can shift left or shift

right Counter with parallel load can

perform count and load.

Internal Hardware Organization

Can be defined by specifying Set of registers and their functions Sequence of microoperations performed on

register data Control that initiates the sequence of

microoperations Can use words to express sequence of

microoperations, but it’s better to use a notation and symbols Register Transfer Language

Registers

Capital letter sometimes followed by a number

MAR– memory address register PC– program counter IR– instruction register R1,R2 – processor register 1, process

register 2 Each flip-flop in a n-bit register is

numbered from n-1 to 0 from left to right.

Register Block Diagram

Register Transfer

Control Function

P: R2 R1 Block Diagram

2nd Register Transfer Example

Bus Transfers

Bus System For 4 Registers

Bus Details

Memory Transfer

Microoperations Summary

Add & Subtract

Arithmetic Microoperations

Binary Adder

4-bit Binary Adder

Binary Adder-Subtractor

Binary Adder-Subtractor

Binary Incrementer

Binary Incrementer

Arithmetic Circuit

4-Bit Arithmetic Circuit

Arithmetic Circuit Function Table

4-Bit Arithmetic Circuit

Logic Micro operations

Special Symbols

16 Logic Micro operations- Part 1

16 Logic Micro Operations – Part 2

Hardware Implementation

One Stage of Logic Circuit

Shift Micro Operations

Logical Shift Example

Circular Shift Example

Arithmetic Shift Example

Shift Micro Operations

Shift Hardware Implementation

4-Bit Combinational Circuit Shifter