8279 Programmable Keyboard Display Interface:
The Intel 8279 is a general purpose programmable keyboard and display I/O interface device designed for use with Intel microprocessors. The Features of 8279 Programmable Keyboard Display Interface are
1. It 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;
Scanned Keyboard Mode
Scanned Sensor Matrix Mode
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
5. The interrupt output of 8279 can be used to tell CPU that the keypress is 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 auto increment 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
10. It provides two output modes for display interface.
Left Entry (typewriter type)
Right Entry (calculator type)
11. Simultaneous keyboard and display operation facility allows to interleave keyboard and display software