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2. Keyboard www.ustudy.in

3. 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 www.ustudy.in

4. 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 www.ustudy.in

5. Multimedia keyboard Remote keyboard www.ustudy.in

6. 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 www.ustudy.in

7. 5 Pin DIN connector 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 The signals are Pin 1 - Keyboard clock Pin 2 - Keyboard data Pin 3 - Not used Pin 4 - Ground Pin 5 - Vcc (+5V) www.ustudy.in

8. Signals Keyboard clock • This provides clock pulse to the keyboard from the system www.ustudy.in

9. Cont., Keyboard data • This is used to send the scan codes from the keyboard to the computer serially. www.ustudy.in

10. Cont., Ground • This is the common ground for all the keyboard circuits www.ustudy.in

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

12. Operations of Keyboard CPU Keyboard Keyboard Controller Keyboard Buffer System Software www.ustudy.in

13. Operations of keyboard • When a key is pressed on the keyboard, it sends a control signal to the keyboard controller. www.ustudy.in

14. Cont., • The keyboard controller generates a code called scan code corresponding to the signal received. www.ustudy.in

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

16. 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 www.ustudy.in

17. The End ….. Thank you ….. www.ustudy.in