VTech Alphabert s Magic Readport User Manual download pdf (Page 55)

BM Dept., Govt. Engg. College, Gandhinagar Page 55

EXPERIMENT NO. 13

AIM: Interface matrix keyboard with 8051. Write program to display key pressed on seven

segment display.

Circuit Diagram:

Interfacing details:

• Rows of matrix keyboard are connected to port pins P1.0 to P1.3

• Columns of matrix keyboard are connected to port pins P2.0 to P2.3

• Common anode seven segment display is connected to port P0

• LEDs are connected to port P1.7 to P1.4 and P2.4 to P2.7. These LEDs may be used to

indicate which row is scanned and which column is read by the program. It may be used

to indicate which key is pressed at present.

Program:

; Program to interface matrix keyboard 4x4. Rows are connected to the Port pins

; P1.0-P1.3 & Columns are connected to Port pins P2.0-P2.3. Rows are grounded

; one by one and read columns

; Seven segment display is connected at port P0

ORG 00h

AJMP START

ORG 13h

RETI

START:

MOV P0,#00h

MOV P2,#0FH ; Port Pins P2.0 to P2.3 i/p pins and P2.4 to P2.7 o/p pins

MOV P1,#00H ;Port P0 output port

REL: MOV P1,#00H ; Make All Rows Ground To Check All Keys

MOV A,P2 ;Read Port P2 To Ensure That All Keys Released

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VTech Alphabert s Magic Readport User Manual Page 55