Lecture 5 - 2/13/2012 1 Functional Functional Components...

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Unformatted text preview: 2/13/2012 1 Functional Functional Components Components of a of a Simple Simple Computer Computer CNIT 17600 – Lecture 5 Readings Chapter 4 NOT 4.10, 4.12, 4.14 2/13/2012 2 Introduction Lecture1 presented a general overview of computer systems In Lecture 2, we discussed how data is stored and manipulated by various computer system components. Lecture 3 described the fundamental components of digital circuits. Lecture 4 described basic data flow through a CPU Having this background, we can now understand how computer components work, and how they fit together to create useful computer systems 3 CPU Basics The computer’s CPU fetches, decodes, and executes program instructions The two principal parts of the CPU are the datapath and the control unit The datapath consists of an arithmetic-logic unit and storage units (registers) that are interconnected by a data bus that is also connected to main memory Various CPU components perform sequenced operations according to signals provided by its control unit 4 2/13/2012 3 CPU Basics Registers hold data that can be readily accessed by the CPU They can be implemented using D flip-flops A 32-bit register requires 32 D flip-flops The arithmetic-logic unit (ALU) carries out logical and arithmetic operations as directed by the control unit The control unit determines which actions to carry out according to the values in a program counter register and a status register 5 The Bus The CPU shares data with other system components by way of a data bus. A bus is a set of wires that simultaneously convey a single bit along each line. Two types of buses are commonly found in computer systems: point-to-point , and multipoint buses. 6 These are point-to- point buses: 2/13/2012 4 Data Bus Components Buses consist of data lines, control lines, and address lines Data lines convey bits from one device to another Control lines determine the direction of data flow, and when each device can access the bus Address lines determine the location of the source or destination of the data 7 Data Bus Components 8 2/13/2012 5 A Sample Bus System Address Bus Encoder/Decoder Data Bus Bus Connected Device Multipoint Bus Multipoint buses are a shared resource Access is controlled through protocols Usually these protocols are built into the hardware 10 2/13/2012 6 Bus Arbitration When multiple devices can be bus master, concurrent requests must be arbitrated Four categories of bus arbitration are: – Daisy chain : Permissions are passed from the highest-priority device to the lowest – Centralized parallel : Each device is directly connected to an arbitration circuit – Distributed using self-detection : Devices decide which gets the bus among themselves – Distributed using collision-detection : Any device can try to use the bus. If its data collides with the data of another device, it tries again 11 Computer Clocks Every computer contains at least one clock that synchronizes the activities of its components A fixed number of clock cycles are required...
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This note was uploaded on 03/04/2012 for the course CNIT 176 taught by Professor Hansen during the Spring '09 term at Purdue University.

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Lecture 5 - 2/13/2012 1 Functional Functional Components...

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