I/O Controllers

Description

I/O controllers (input/output controllers) are devices, which interface between an input or output device and the computer or hardware device; they can also be functional units that control one or more input-output channels. They are also termed as an input/output interface (IOC), a parallel input/output control, or peripheral input/output controllers (PIOC). They are usually present on the motherboard. I/O controllers comprise three types of internal registers namely, status register, data register, and a command register.

Functions

The functions of I/O controllers are:

• Receiving input and output signals from a central processor and sending specific control signals to the device they control
• Manage the dataflow to and fro from the device to make the central processor free from involvement in each device control

Need for I/O controllers

• Various I/O devices have diverse characteristics and when they are directly connected, CPU responds appropriately to each device but a lot of time is spent by them in interacting with each and every I/O device and thus less time is available for executing user programs. If I/O controllers are employed, they provide low level machine-understandable commands and data for the proper operation of the associated I/O device
• The amount of electrical power used to send signals on a system bus is very low by using I/O controllers
• Considerably reduces wiring

Applications

Low voltage I/O controllers are used for monitoring and controlling low voltage devices such as outdoor lights, alarm systems, appliance systems, and contact closures. Super I/O controllers are used for serial port control, parallel port control and floppy disk drive control. Industrial I/O controllers are used for control and data acquisition applications where there is need for PLC style programming. Ethernet I/O controllers access remote RS-232 or RS-485 technologies and are suitable for digital outputs and also for reading digital outputs on server.