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Question 11.5: Assume that the INT1 pin is connected to a switch that is no...

Assume that the INT1 pin is connected to a switch that is normally high. Whenever it goes low, it should turn on an LED. The LED is connected to P1.3 and is normally off. When it is turned on it should stay on for a fraction of a second. As long as the switch is pressed low, the LED should stay on.

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ORG    0000H
LJMP   MAIN            ;by-pass interrupt

   ;vector table

;- – ISR for INT1 to turn on LED

ORG   0013H             ;INT1 ISR
SETB   P1.3                ;turn on LED
MOV    R3,#255

BACK:         DJNZ    R3,BACK      ;keep LED on for a while

CLR    P1.3                ;turn off the LED
RETI                          ;return from ISR

;- – MAIN program for initialization

ORG   30H

MAIN:          MOV   IE,#10000100B  ;enable external INT 1
HERE:         SJMP   HERE          ;stay here until get interrupted

END

 

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