Digital Systems Design 1 Basic Organization of Digital

Digital Systems Design 1 Basic Organization of Digital Computers 12/5/2020 Veton Këpuska 1

Objective of the Course o o o Emphasis on the Designer’s Point of View Design carried out through a hardware description language (AHPL) for specifying the control sequence. Control Sequence is a step-by-step description of the functioning of the digital system. Control Sequences are easily translated into control unit hardware. With completion of Control Sequence Digital System is considered designed. 12/5/2020 Veton Këpuska 2

Generic Digital System Vectors of Binary Information Control Information 12/5/2020 { Digital System Veton Këpuska 3

Brief Overview of Computer Evolution o From Abacus to Mechanical Calculators Designed in 17 th Century by Pascal and Leibniz. o First Device that is considered a computer in modern sense was proposed by Charles Babbage in 1830 (Analytical Engine). o Howard Aiken of Harvard University in 1937 proposed Automatic Sequence Controlled Calculator -> Mark I sponsored by Harvard and IBM. Completed in August 7, 1944. Mark I was electromechanical machine. o ENIAC first Digital Computer based on Vacuum Tubes: J. P. Eckert and J. W. Mauchly, and John von Neumann mathematical consultant. n n n o Great Speed of Electronic Devices => Unnecessary to have many parallel calculating elements. Storing the Program in Memory much the same manner as data => made possible to branch to alternate sequences of instructions. New Developments in electronics => EDVAC Von Neumann’s 5 basic principles that defines a computer: 1. 2. 3. 4. 5. It must have an input medium, by means of which an essentially unlimited number of operands or instructions may be entered. It must have store, from which operands or instructions may be obtained and into which results may be entered, in any desired order. It must have a calculating section, capable of carrying out arithmetic or logical operations on any operands taken from the store. It must have an output medium, my means of which an essentially unlimited number of results may be delivered to the user. It must have a control unit, capable of interpreting instructions obtained from memory, and capable of choosing between alternative courses of action on the bases of computed results. o Eckert and Mauchly developed first commercially produced computer – UNIVAC I (1951). o Von Neumann at Princeton led development of IAS (1951) n Indexing and indirect addressing. 12/5/2020 Veton Këpuska 4

Basic Organization of Digital Computers Input CPU Memory Output Processing (ALU) Control Data and Instructions Results/Data Instructions Control Signals Decision Results 12/5/2020 Veton Këpuska 5

Memory o o o Word Length (8 bits – 128 bits) Address Space (16 bits => 64 K Memory) Access Speed n n 12/5/2020 Fast – Cache (Pentium 4 - 512 K) RAM (512 M) Hard Disk Space (>100 G) Slow (CD, DVD, Tape, etc. ) Veton Këpuska 6

Computer Categorization o Based on Use, Speed … n n n 12/5/2020 Personal Devices (PDA’s) Microcomputers (Desktop, Laptop) Mainframes (Business Machines) Supercomputers Parallel Computer Systems Veton Këpuska 7

Instruction Formats o Instruction Word is divided into several sections/fields each containing one of the following: n n 12/5/2020 Op-code: indicating the operation (ADD, SUB, SHIFT, …) Operand Address(es). Result Address Next Instruction Address Veton Këpuska 8

Typical Instruction Set Formats o 4 address instruction Operand Opcode o Operand Address Instruction Address Result or Instruction Address 2 address instruction Opcode o Address 3 address instruction Opcode o Address Result Address Operand Address 1 address instruction Opcode 12/5/2020 Operand or Instruction Address Veton Këpuska 9

Software o Increasing level of abstraction : n n o Hardware Instruction Set Assembly Compilers/Interpreters of High Level Languages: (C, C++, Java, Fortran, etc. ) Applications Operating Systems (Interface between hardware and application software) 12/5/2020 Veton Këpuska 10

Hardware Description o o Objective of the course – Define a Computer (RIC) and design its subsystems via a Hardware Description Language: AHPL Alternative to AHPL is VHDL – a more powerful language. n n n 12/5/2020 VHDL intended to be used over all levels of hardware description: from the digital circuit to the abstract algorithm. This is the reason that it could not be tailored for clock-mode description as was AHPL Thus it is ill suited to be used in the context of this text book. Veton Këpuska 11