DON’T JUST SIT THERE. YOU CAN LEARN INPUT OUTPUT INTERFACE IN QUICK 15 MINUTES.

Contents Input Output Interface I/O Bus and Interface Modules I/O versus Memory Bus Isolated (Port-Mapped) versus Memory-Mapped I/OExample of I/O Interface

Input Output Interface Internal storage & External I/O DevicesDirect Communication is not possible.The major differences are:

Different manner of operation Data transfer rate Difference in word format Difference in operating modes of peripherals

I/O Bus & Interface Module

Interface Interface

Interface

Interface

Keyboard &

Display Terminal

Printer Magnetic Disk

Magnetic Tape

DataAddressControl

I/O BusProcessor

Fig. Connection of I/O Bus to input-output devices

IO CommandsThere are four types of I/O Command:

Control Command Status Command Output Data Command Input Data Command

I/O Versus Memory BusLike I/O Bus, Memory Bus also contains Data, Address & Control Lines.

Three ways to communicate: Use two separate buses Use one common bus but separate control lines Use common bus with common control lines

Isolated versus Memory-Mapped I/OISOLATED I/O MEMORY MAPPED I/O

Separate read/write control lines

A single set of read/write control lines

Separate memory and I/O address spaces

Common address space

Distinct input & output instructions

No Specific input or output instructions

- Considerable flexibility in handling I/O

operations

Example of an I/O InterfaceI/O DataBus

Buffers

Status Register

ControlRegister

Port BRegister

Port ARegister

CSRS1RS0RDWR

Timing &

Control Signal

Inte

rnal

Bus

Bidirectional

Data BusChip Select

Register SelectI/O ReadI/O Write

To CPU To I/O Device

Control

I/O Data

Status

Fig. Example of an I/O Interface Unit

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