The document describes an 8279 keyboard/display interface chip. It contains: - Bi-directional data and control lines to interface with a microprocessor. - Keyboard debounce and control logic with an 8x8 FIFO to store pressed keys. - Display control with a 16x8 display RAM to drive an 8-digit 7-segment display. - Registers to control the display timing and scanning of the keyboard matrix rows.

1. 8279
KEY BOARD/DISPLAY INTERFACE 1
SREE

2. KEY BOARD/DISPLAY INTERFACE 2


3. KEY BOARD/DISPLAY INTERFACE 3

4. KEY BOARD/DISPLAY INTERFACE 4
DATA
BUFFERS
I/O
CONTROL
FIFO/
RAM
INTERNAL DATA BUS
DISPLAY ADDRESS
REGISTER 16X8 DISPLAY CONTROL AND
TIMING
REGISTERS
8X8
FIFO/SENS
OR RAM
KEYBOARD
DEBOUNCE
AND
CONTROL
DISPLAY REGISTER
TIMING
AND
CONTROL
SCAN COUNTER RETURN
CLK RESET
DB0 -DB7 RD WR CS A0 IRO
8
OUT A0 -A3 OUT B0-B3
BD SL-0SL3 RL-0RL7
SHIFT
CNTL/STB

5. KEY BOARD/DISPLAY INTERFACE 5
A0 RD WR OPERATION
0 0 0 MPU WRITES THE DATA IS 8279
0 0 1
MPU READS THE DATA FROM
8279
1 1 0
MPU WRITES CONTROL WORD TO
8279
1 0 1
MPU READS STATUS WORD FROM
8279

6. KEY BOARD/DISPLAY INTERFACE 6
BI-DIRECTIONLA DATA BUFFER DB0 -DB7
I/O CONTROL LINES….RD WR CS A0
 A0 TRANSMIT/RECEIVE CONTROL WORD
OR DATA
 ACTIVE HIGH IRQ LINE GENERATED
WHEN EVER THE DATA AVAILABLE

7. KEY BOARD/DISPLAY INTERFACE 7
HAS KEYBOARD DEBOUNCE AND CONTROL ,8X8
FIFO/SENSOR RAM
TYPES
TWO KEY LOCK OUT
N KEY ROLL OVER
IN 2KEY …TWO KEYS ARE PRESSED
SIMELTANEOUSLY
FIRST KEY ONLY RECONGANIZED
IN N KEY…STORES CODE IN INTERNAL BUFFER

8. KEY BOARD/DISPLAY INTERFACE 8
CONNECTED IN ROWS OF MATRIX
SCAN COUNTER AND SCAN LINES…(SL-0SL3 )
THESE LINES DECODED BY 4 TO 16 DECODER GENERATE 16
SCAN LINES
DISPLAY SECTION:
TWO GROUPS OF OUT PUT LINES
SEND DATA AND DIPLAY DRIVES
BLANK THE DISPLAY
16X8 DISPLAY RAM

9. KEY BOARD/DISPLAY INTERFACE 9
4100H MVI A,00H MODE & DISPLAY SET
4102H MVI
A,OOH
4104H MVI A,CC
H
4106H OUT C2 CLEAR & DISPLAY
4108H MVI A,
90H
410AH OUT C2
410CH MVI A,O8H DISPLAY “ 8”
410EH OUT C0
4110H MVI A,FF H BLANK THE REST OF THE DISPLAY
4112H OUT C0
4114H OUT C0
4116H OUT C0
4118H OUT C0
411AH OUT C0
411CH HLT

10. KEY BOARD/DISPLAY INTERFACE 10

11. KEY BOARD/DISPLAY INTERFACE 11
THROUGH EIGHT COMMAND
WORDS