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25. Programmed I/O Overview

The chapter discusses the intricacies of Input/Output (I/O) operations, focusing on programmed I/O techniques and the necessity of I/O modules. It outlines the requirements for I/O commands, addressing schemes, and the distinction between memory-mapped I/O and isolated I/O. The significance of I/O modules is emphasized due to their need for managing diverse devices without directly connecting them to the CPU.

Sections

Programmed I/O Overview

This section provides an overview of programmed I/O, outlining the steps involved in CPU-I/O device communication, the polling mechanism’s inefficiency, and I/O addressing schemes.

25.1 Section Overview

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25.1.1 Problems with Polling

The section discusses the inefficiencies of polling in CPU operations, particularly in the context of I/O operations.

25.1.2 Steps in Programmed I/O

This section discusses the key steps involved in programmed I/O, highlighting the need for status checking and data transfer, while addressing CPU inefficiencies.

25.1.3 Basic Requirements for I/O Operations

This section discusses the basic requirements for input/output operations, including programmed I/O and I/O addressing schemes.

I/O Command Issues

This section covers the status checking mechanisms of input/output operations, highlighting the challenges of CPU polling and introducing programmed I/O functionality.

25.2 Section Overview

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25.2.1 Identifying the I/O Module

This section details the processes involved in interacting with Input/Output (I/O) modules, focusing on programmed I/O techniques and addressing schemes.

25.2.2 Control Commands

This section covers the significance and mechanics of control commands in I/O operations, including programmed I/O and the addressing schemes for devices.

25.2.3 Mode of Transfer

This section discusses the mechanisms by which data transfer occurs between the CPU and I/O devices, including programmed I/O and the significance of addressing and control commands.

25.25.2.4 Categories of I/O Commands

This section explains the categories of I/O commands, highlighting the differences between programmed I/O, memory mapped I/O, and isolated I/O in data transfer.

Addressing I/O Devices

This section discusses the methods for managing input/output devices within a computer system, focusing on programmed I/O, addressing schemes, and the roles of I/O modules.

25.3 Section Overview

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25.3.1 Addressing Scheme

This section discusses the addressing scheme used in I/O operations, emphasizing the difference between memory-mapped and isolated I/O.

25.3.2 Mapping I/O Devices

This section discusses the mapping of I/O devices to a CPU, including programmed I/O and the differences between memory-mapped and isolated I/O.

25.3.3 Memory-Mapped I/O vs Isolated I/O

This section discusses the differences between memory-mapped I/O and isolated I/O, explaining how they manage device communication with the CPU.

I/O Command Execution

This section covers the essentials of I/O command execution, focusing on programmed I/O techniques, addressing schemes, and the differences between memory-mapped and isolated I/O.

25.4 Section Overview

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25.4.1 Functionality of Memory-Mapped I/O

This section discusses the functionality of memory-mapped I/O, focusing on the communication between CPU and I/O devices, the addressing schemes, and their significance.

25.4.2 Functionality of Isolated I/O

This section discusses the functionality of isolated I/O in computer systems, including its operations, addressing schemes, and differences from memory-mapped I/O.

25.4.3 Special I/O Commands

This section discusses the mechanisms and commands used for Input/Output (I/O) operations in computer processing, focusing on programmed I/O and different addressing schemes.

Device Service Routine

This section provides an overview of programmed input/output operations and how CPUs interact with I/O devices through service routines.

25.5 Section Overview

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25.5.1 Execution of Device Service Routine

The section discusses the mechanics of executing a device service routine, focusing on programmed I/O and interaction between the CPU, I/O module, and devices.

Test Items

This section covers the fundamentals of I/O operations, including programmed I/O, the use of I/O modules, and the addressing schemes used for I/O devices.

25.6 Section Overview

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25.6.1 Questions Addressing Objectives

This section discusses programmed I/O, its challenges, addressing schemes, and the steps involved in I/O operations.

Learning Objectives

  • CPU cannot multitask while waiting for I/O operations, leading to wasted processing time.

  • I/O modules manage communication between the CPU and devices, enabling efficient data transfer.

  • Two primary addressing schemes for I/O devices exist: memory-mapped I/O and isolated I/O.

Key Concepts

Programmed I/O

A method of I/O transfer where the CPU actively waits and checks the status of I/O devices to proceed with data transfer.

I/O Modules

Components that facilitate communication between the CPU and I/O devices, essentially acting as intermediaries to offload tasks from the CPU.

MemoryMapped I/O

A system where I/O devices share the same address space as memory, allowing the CPU to communicate with devices using standard read and write instructions.

Isolated I/O

A scheme where I/O devices have a separate address space from memory, requiring specific control signals to access either memory or I/O devices.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting