Features of 8279

Features of 8279

AU : May.-04, 16, Dec.-13, 14

1. IC 8279 provides a scanned interface to a 64-contact key matrix, with two more keys CONTROL and SHIFT.

2. It provides three input modes for keyboard interface.

i) Scanned Keyboard Mode

ii) Scanned Sensor Matrix Mode

iii) Strobed Input Mode

3. It has built-in hardware to provide key debounce.

4. It allows key depressions in 2 key lockout or N-key rollover mode, which eliminates software required to implement 2 key lockout and N-key rollover modes.

5. The interrupt output of 8279 can be used to tell CPU that the keypress is detected. This eliminates the need of software polling.

6. It provides 8 byte FIFO RAM to store keycodes. This allows to store 8 key board inputs when CPU is busy in performing his own computation.

7. It provides multiplexed display interface with blanking and inhibit options.

8. It provides sixteen byte display RAM to store display codes for 16 digits, allowing to interface 16 digits.

9. In autoincrement mode, address of display RAM and FIFO RAM is incremented automatically which eliminates extra command after each read/write operation to access successive locations of display RAM and FIFO RAM.

10. It provides two output modes for display interface.

i) Left Entry (typewriter type)

ii) Right Entry (calculator type)

11. Simultaneous keyboard and display operation facility allows to interleave keyboard and display software.

Review Questions

1. Explain the advantages of using the following chips in microprocessor based systems :

i) Keyboard and

ii) Display controller.

AU : May.-04, Marks 6

2. Explain features of 8279 keyboard/display controller.

AU : Dec.-13, Marks 8, May-16, Marks 16

3. Explain about 8279 keyboard display controller in detail.

 AU : Dec.-14, Marks 16