IO organization

Question 1

Input/Output Subsystem

Answer 1

It handles all the input and output operations of the computer system.

Question 2

Peripheral Devices

Answer 2

Input or output devices that are connected to computer are called peripheral devices

Question 3

types of peripherals

Answer 3

Input devices: they allow user input, from the outside world into the computer. Examples: keyboard, mouse, speech recognition, sensor, etc.
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Output devices: they allow information output, from the computer to the outside world. Examples: printer, monitor (display unit), speaker, etc.
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Auxiliary storage devices: these are used for permanent storage of data. Examples: magnetic tape, magnetic disk, optical disk, flash drive

Question 4

Input/Output Interface

Answer 4

Input/Output Interface provides a method for transferring information between internal system (CPU) and external I/O devices (peripheral devices)

Question 5

Significance of I/O Interface

Answer 5

1.Peripherals are electromechanical and electromagnetic devices and their manner of operation is different from the operation of the CPU and memory, which are electronic devices.
2.The data transfer rate of peripherals is usually slower than that of the CPU, and consequently, a synchronization mechanism may be needed.
3.Data codes and formats (bytes) in peripherals differ from the word formats in the CPU and memory.

Question 6

what does the IO bus consist of

Answer 6

data lines, address lines, and control lines.

Question 7

functions of interface

Answer 7

a)
decodes the device address
b)
decodes the commands from the processor
c)
provides signals for the peripheral controller
d)
synchronizes the data flow and supervises the transfer rate between peripheral and CPU or memory

Question 8

Types of commands that an interface may receive

Answer 8

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Control command – is used to activate the peripheral and inform it on what to do
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Status command – is used to test various conditions in the interface and peripheral
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Data output command – causes the interface to respond by transferring data from the bus into one of its registers
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Data input command – is the opposite of the data output command. In this case, the interface receives data from the peripheral and places it in its register

Question 9

Device Controllers

Answer 9

Device Controllers are components on the motherboard (or on an expansion card) that acts as an interface between the CPU and the actual device

Question 10

Interrupt Request (IR)

Answer 10

When a device needs to access the CPU, the device controller issues an Interrupt Request (IR) to the CPU in order for the CPU to stop the current task and start communicating with the peripheral device

Question 11

functions of device controllers

Answer 11

It handles the data flow between the processor and the device it is connected to.
It translates signals from the device into the format that can be understood by the CPU, and vice-versa.
It buffers data being sent between the device and the CPU.
The device Controller also performs synchronization and error detection

Question 12

Examples of Device Controllers

Answer 12

Keyboard Controller – controls the keyboard
DMA Controller – controls Direct Memory Access
Network Adaptor Controller – controls Network Interface Card (network adapter)
IDE Controller – controls hard disk and CD/DVD drive
Graphics Adapter Controller – controls video output devices such as monitor, projector
USB Controller – controls devices connected by USB

Question 13

Ways that the computer buses can be used by CPU to communicate with memory and I/O

Answer 13

1.
Use of two separate buses, one for memory and the other for I/O. In this method, all data, address and control lines would be separate for memory and I/O. Both I/O and memory have different sets of address spaces and instructions but require more buses.
2.
Use of one common bus for both memory and I/O but with separate control lines for each. This configuration is called Isolated I/O.
3.
Use of one common bus for both memory and I/O with a common control line. This configuration is called Memory mapped I/O.

Question 13

Memory mapped I/O and Isolated I/O.

Answer 13

methods to perform input/output operations between the CPU and peripheral devices in the computer

Question 14

Memory-mapped I/O

Question 14

Isolated I/O

Answer 14

When the CPU fetching or transferring an I/O data, it places the address associated with the data on the common address lines. At the same time, it enables the I/O read (for input) or I/O write (for output) control line. This informs the components connected to the common bus that the address in the address line is for an I/O register and not for a memory word

Question 15

Input/Output Processor

Answer 15

is a processor separate from the CPU designed to handle only I/O operations

Question 16

Asynchronous Data Transfer

Answer 16

the two units are said to be asynchronous to each other, and if data transfer occurs between them, this data transfer

Question 16

Synchronous Data Transfer

Answer 16

It is when transfer between two units registers in the I/O interface share a common clock with CPU registers

Question 16

Modes of I/O Data Transfer

Answer 16

1. Programmed I/O
2. Interrupt Initiated I/O
3. Direct Memory Access.

Question 17

method used is to disable the buses

Answer 17

➢
Bus Request (BR) – it is used by the DMA controller to request the CPU to relinquish the control of the buses.
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Bus Grant (BG) – it is activated by the CPU to inform the DMA controller that the buses are in a high impedance state and the requesting DMA controller can take control of the buses. Once the DMA has taken the control of the buses, it transfers the data

Question 18

Bus Arbitration

Answer 18

Bus arbitration is the process of resolving conflicts that arise when multiple devices attempt to access the bus at the same time

Question 19

Applications of bus arbitration in computer organization

Answer 19

Shared Memory Systems: Bus arbitration allows multiple devices to access the memory without interfering with each other.
Multi-Processor Systems: Bus arbitration allows multiple processors to share access to the bus to communicate with each other and with shared memory.
Input /Output Devices: Bus arbitration allows multiple input/output devices to share access to the bus to communicate with the processor and memory.

Question 20

bus

Answer 20

is a connected common communication pathway

Question 21

Bus master

Answer 21

Is a device that can transfer data on the bus at the same time

Question 22

Approaches to bus arbitration

Answer 22

centralized arbitration, a single
device (arbiter) is responsible for performing the required arbitration
distributed arbitration, all devices compete for access to the
bus by sending a request signal and waiting for a grant signal