8051 Program – addition 16bit

; 16bit addition
; R6 R7
; + R4 R5
; = R1 R2 R3
; Add the low bytes R7 and R5, leave the answer in R3
; Add the high bytes R6 and R4, adding any carry from step 1, and leave the answer in R2.
; Put any carry from step 2 in the final byte, R1
	ORG 0H
MAIN:
	MOV R6,#1AH	;Load the first value into R6 and R7
	MOV R7,#44H
	MOV R4,#22H	;Load the second value into R4 and R5
	MOV R5,#0DBH
	LCALL ADD_16
	SJMP MAIN
ADD_16:
		; step 1
	MOV A,R7	;Move the low-byte into the accumulator
	ADD A,R5	;Add the second low-byte to the accumulator
	MOV R3,A	;Move the answer to the low-byte of the result
		; step 2
	MOV A,R6	;Move the high-byte into the accumulator
	ADDC A,R4	;Add the second high-byte to the accumulator, plus carry from step 1.
	MOV R2,A	;Move the answer to the high-byte of the result
		; step 3
	MOV A,#00h	;By default, the highest byte will be zero.
	ADDC A,#00h	;Add zero, plus carry from step 2.
	MOV R1,A	;Move the answer to the highest byte of the result
	RET
	END

; add two 2 byte numbers
; register operation
	ORG 0H
	MOV R1,#12
	MOV R2,#34
	MOV R3,#56
	MOV R4,#78	;3412+7856 = 0AC68
	MOV R7,#00	;3rd byte=0
	CLR C
	MOV A,R1
	ADD A,R3
	MOV R5,A
	MOV A,R2
	ADDC A,R4
	MOV R6,A
	JNC SKIP
	MOV R7,#01	;3rd byte=1
SKIP:	SJMP $
	END

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Related topics:
8051 Program - arithmetic operation 8bit   |   8051 Program - addition 8bit   |   8051 Program - subtraction 8bit   |   8051 Program - multiplication 8bit   |   8051 Program - division 8bit   |   8051 Program - subtraction 16bit   |   8051 Program - multiplication 16bit   |   8051 Program - division 16bit   |   8051 Program - addition multibyte   |   8051 Program - multiplication 16bit by 8bit   |   8051 Program - addition 8bit 2digit bcd   |   8051 Program - memory subroutines   |   8051 Program - math subroutines   |   8051 Program - conversion subroutines

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List of topics: 8051

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