Keyboard

Introduction Keyboard is an input device. It is used to give text, numbers and controls as input to computer. The keyboard resembles the structure of ordinary typewriter keyboard with some additional keys

Types of keyboard PC/PC-XT keyboard-83 keys PC-AT keyboard-84 keys Enhanced PC-AT keyboard-101 keys Windows keyboard-114 keys Remote keyboard-109 keys

Multimedia keyboard Remote keyboard

Keyboard signals The keyboard is connected to the system board (Motherboard) through a flexible standard DIN connector. There are two types of DIN connectors 5 PIN DIN connector 6 PIN DIN connector

5 Pin DIN connector The signals are Pin 1 - Keyboard clock Pin 2 - Keyboard data Pin 3 - Not used Pin 4 - Ground Pin 5 - Vcc (+5V) 6 Pin DIN connector The signals are Pin 1 - Keyboard data Pin 2 - Not used Pin 3 - Ground Pin 4 - Vcc (+5V) Pin 5 - Keyboard clock Pin 6 - Not used

Signals Keyboard clock This provides clock pulse to the keyboard from the system

Cont., Keyboard data This is used to send the scan codes from the keyboard to the computer serially.

Cont., Ground This is the common ground for all the keyboard circuits

Cont., Vcc (+5V) This will provide the required supply for the operation of keyboard. The Keyboard clock lone and keyboard data line are bidirectional.

Operations of Keyboard

Operations of keyboard When a key is pressed on the keyboard, it sends a control signal to the keyboard controller.

Cont., The keyboard controller generates a code called scan code corresponding to the signal received.

Cont., This code is placed in the keyboard buffer and it sends interrupt signal to the CPU through the system software

Cont., The CPU stop its current execution and reads the scan code from the keyboard buffer. Then it converts the scan code into ASCII form

The End ….. Thank you …..