Chapter Five INPUT/OUTPUT 1
Outline Introduction External Devices I/O Modules Techniques for I/O operations Programmed I/O Interrupt-Driven I/O Direct Memory Access I/O Channels and Processors
Introduction The computer system’s I/O architecture is its interface to the outside world. This architecture provides a systematic means of Controlling interaction with the outside world and providing the operating system with the information it needs to manage I/O activity effectively
Introduction It is the third key element (IO module) of a computer system next to processor and memory Each module interfaces to the system bus or central switch and controls one or more peripheral devices. It contains logic for performing a communication function between the peripheral and the bus
Why IO MODULE??? Varity of methods of operation (with the processor) Slow/fast data transfer rate use different data formats and word lengths 5
Generic Model of an I/O Module 6
I/O module has two major functions Interface to the processor and memory via the system bus or central switch Interface to one or more peripheral devices by tailored data links 7
EXTERNAL DEVICES Human readable Machine readable Communication 8
External Device An external device attaches to the computer by a link to an I/O module The link is used to exchange control, status, and data between the I/O module and the external device. An external device connected to an I/O module is often referred to as a peripheral device or, simply, a peripheral 9
Categories Human readable: Suitable for communicating with the user Example: VDTs and printers Machine readable: Suitable for communicating with equipment Example: magnetic disk and tape systems, and sensors and actuators, such as are used in a robotics application Communication: Suitable for communicating with remote devices 10
Block Diagram of an External Device 11
Control signals Determine the function that the device will perform, such as : Send data to the I/O module (INPUT or READ), Accept data from the I/O module (OUTPUT or WRITE), Report status perform some control function particular to the device (e.g., position a disk head).
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- Fall '19
- Central processing unit, Input device