Computer Operating System Study note _ 12_ I/o management-I/O management overview

I/O management-I/O management overview

I,I/OControl Mode

1. I/O device Concept

I/O device: DivisionController,Timer(Central processor) andMemoryAll other devices, also known as external devices.

I/O operation: data transmission between memory and peripheral media.

2. I/O device category

(1) classification by interaction objects: Human-Computer Interaction devices.

(2) classification by interaction direction: input and output devices.

(3) classification by peripheral features: block transmission devices or character transmission devices.

3. I/O management objectives

The device management function is to assign and use devices according to the structure and device type of the I/O subsystem.

The goal of device management is to improve efficiency, facilitate use, and facilitate control.

4. I/O application interface

Provides user interfaces for devices:Command INTERFACEAndProgramming Interface.

Device allocation and release: before using the device, you need to allocateDeviceAnd correspondingChannel,Controller.

Device Access and control: includingConcurrent accessAndError Handling.

 I/OBuffering and Scheduling: The target isImproveI/OAccess efficiency.

5. I/O interface control mode

One of the main tasks of device management is to controlDeviceAndMemory or processorBetweenData TransmissionThere are four I/O control methods between the peripheral device and the memory, as described below.

(1) program Access Control Method

(2) interrupt control method

(3) DMA [Direct Memory addressing] Mode

[DMA and interrupt control frees the CPU from a lot of useless work]

(4) channel mode

[Von noriman computer system: memory, controller, memory, I/O device]

II,I/OSoftware hierarchy

1. I/O software goals

(1) device independence.

(2) Uniform Naming.

2. I/O software hierarchy

In I/O software, lower layers process hardware-related details and isolate hardware features from higher layers; the higher layer provides users with a friendly, clear and regular I/O interface.

The general I/O software structure is divided into four layers.

User Layer

Independent device layer(Operating System)

Device Driver

Interrupt handling program

Interrupt handling program: the interrupt method of the I/O device is controlInput/output deviceAndMemory andCPUThe main method of data transmission. Device Driver: I/O device driver isDeal with hardware directlySoftware Module.

[Interrupt processing programs and device drivers are generally completed by hardware developers]

Device independent layer: in I/O software, most of the Software except the device driver is not related to the device.

User-layer software:System CallOrAPI. The general I/O system calls are implemented by the library process.

Computer Operating System Study note _ 12_ I/o management-I/O management overview