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

2 nd 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