VTech Alphabert s Magic Readport User Manual download pdf (Page 69)

BM Dept., Govt. Engg. College, Gandhinagar Page 69

Program: Write a program to rotate DC motor connected in above circuit such that when switch

SW1 is pressed, motor rotates in clockwise direction and when SW2 is pressed, motor rotates in

anti-clockwise direction. Use external interrupts for the program.

ORG 00h

AJMP START

ORG 03h ; Vector location for external interrupt 0

SETB P1.1 ; Rotate motor in clockwise direction

CLR P1.0 ; -- do --

RETI

ORG 13h ; Vector location for external interrupt 1

SETB P1.1 ; Rotate motor in anticlockwise direction

CLR P1.0 ; -- do --

RETI

START: CLR P1.0 ; Make P1.0 output pin

CLR P1.1 ; Make P1.1 output pin

CLR P1.2 ; Make P1.2 output pin

MOV IE,#85h ; Enable external interrupt 0 and 1

SETB IT0 ; Negative edge triggered interrupt

SETB IT1 ; Negative edge triggered interrupt

SETB P1.0 ; Enable chip L293 (H-bridge)

HERE: SJMP HERE

:: WORKSHEET ::

A. Modify previous program without using interrupts.

(Hint: using polling method to check whether switch is pressed or not like JNB P3.2,

clockwise.)

Memory

Location

HEX

code

Label Opcode Operands Comments

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 79 80

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VTech Alphabert s Magic Readport User Manual Page 69