INPUT/OUTPUT ARCHITECTURE

Input/Output Devices

I/O CAN BE CHARACTERIZED BY
::behaviour; input, output, storage
::partner; human or machine
::data rate; bytes/sec, transfer/sec

I/O bus connection

iNPUT/oUTPUT MODULE

• Interface to CPU and Memory
• Interface to one or more peripherals

GENERIC MODEL of I/O MODULE

FUNCTION OF I/O MODULES

1. Control and Timing

• CPU asks I/O module to check the status of attached device.
• I/O module tells the status
• CPU requests for data transfer to I/O module if device is ready
• I/O module gathers the data and transfer to the CPU

 2.  CPU Communicating

• Command decoding
• Data- Exchange between CPU and Module
• Status reporting - to CPU, since peripherals are slow
• Address recognition for the devices connected to it

 3. Device Communication

• May involves command, status information and data transfer

 4. Data Buffering

• Essential function to overcome speed mismatch

 5. Error Detection

• Like paper jam, bad data etc.

I/O MODULE STRUCTURE

INPUT/OUTPUT SYSTEM CHARACTERISTICS

• Dependability
• Performance measures

dependability

TECHNIQUES OF I/O