Microcontroller introductory program 1

;Experiment name:       Flashing light experiment               ;
;Author:             Long Yi                   ;
;Version:             VER 1.0                 ;
;Description:  An introductory experiment for beginners to learn microcontroller programming       ;
;Modification:               None                    ;
;Programming language:        Assembly language                ;
;Programming date:       2010-04-12              ;

;************************************************;

method one:

       ORG  00H
START:  CLR  P0.0      ;P0.0 is set to 0, making the LED light up
      CALL  DELAY    ;Call the delay subroutine
      SETB  P0.0    ;P0.0 is set to 1, making the LED off
      CALL  DELAY    ;Call the delay subroutine
      JMP  START    ;Return to loop
DELAY:  MOV  R5,#20   ;Using a crystal oscillator of 12MHZ, the delay time of this delay subroutine is 0.2 seconds
D1:    MOV  R6,#20
D2:     MOV  R7,#248
      DJNZ  R7,$
      DJNZ  R6,D2
      DJNZ  R5,D1
      RET
       END

Method Two:

      ORG  00H
START:  CPL  P0.0    ; Invert bit P0.0 to make the LED turn on and off alternately
       CALL  DELAY    ; Call the delay subroutine
      JMP  START    ; Return to loop
DELAY:  MOV  R5,#20   ; Using a 12MHZ crystal oscillator, the delay time of this delay subroutine is 0.2 seconds
D1:    MOV  R6,#20
D2:     MOV  R7,#248
      DJNZ  R7,$
      DJNZ  R6,D2
      DJNZ  R5,D1
      RET
      END