; https://www.electronicshub.org/8051-microcontroller-assembly-language-programming/
;
$DATE (03.12.2020)
$TITLE (Example 2: Blinking LEDs )
$PAGELENGTH(56)
$PAGEWIDTH(150)
$DEBUG
$XREF
$NOLIST
$MOD51
$LIST
;
ORG 00H 			; Assembly Starts from 0000H.
; Main Program
START:	MOV P1, #255	  ; Move 11111111 to PORT1.
		   LCALL WAIT 	     ; Call WAIT 
		   MOV A, P1 	     ; Move P1 value to ACC 
		   CPL A 		       ; Complement ACC
		   MOV P1, #0 	     ; Move ACC value to P1
		   LCALL WAIT 	     ; Call WAIT
		   SJMP START 	   ; Jump to START
WAIT:  PUSH ACC
       PUSH   PSW
	     MOV R2, #8 	 ; Load Register R2 with 10 (0x0A)
WAIT3:	MOV R3, #255 	 ; Load Register R3 with 10 (0xC8)
WAIT2:	MOV R4, #255 	 ; Load Register R4 with 10 (0xC8)
WAIT1:	DJNZ R4, WAIT1	  ; Decrement R4 till it is 0. Stay there if not 0.
		   DJNZ R3, WAIT2  ; Decrement R3 till it is 0. Jump to WAIT2 if not 0.
		   DJNZ R2, WAIT3  ; Decrement R2 till it is 0. Jump to WAIT1 if not 0.
		   POP PSW
       POP ACC   
       RET 		         ; Return to Main Program
END  				           ; End Assembly