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Input (Keyboard) Modes

8279 has three input modes such as scanned keyboard, scanned sensor matrix, and strobed input.

Scanned Keyboard
 In this mode, 8279 can be encoded (8 × 8 key keyboard) or decoded (4 × 8
key keyboard) scan lines. A key depression generates a 6-bit encoding of key position. Position and shift and control status are stored in the FIFO. Keys are automatically debounced with 2-key lockout or N-key rollover.


Scanned Sensor Matrix In this mode, a sensor array will be interfaced with 8279 with encoded (8×8 matrix switches) or decoded (4 × 8 matrix switches) scan lines. Key status are stored in RAM addressable by CPU.


Strobed Input Data on return lines during control line strobe is stored in the FIFO.


Output (Display) Modes

8279 provides two output modes such as display scan and display entry.


Display Scan In this mode, Programmable Key Board and Display Controller, 8279 provides 8 or 16 character multiplexed displays that can be organised as dual 4-bit or single 8-bit (B
0 = D0, A3 = D7) display unit.

Display Entry Right entry or left entry display formats are executable for 8279 IC.


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