Write a 3-byte binary addition subroutine-EEWORLD

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A simple experimental programming question for the microcontroller: write a 3-byte binary addition subroutine.

The program entry is:
addend 1: 22H, 21H, 20H three bytes, 22H is the highest bit;
addend 2: 32H, 31H, 30H three bytes, 32H is the highest bit.
The program exit is:
sum: 23H, 22H, 21H, 20H four bytes, 23H is the highest bit.

Best answer:

The addend has three bytes and the addresses are continuous, so just loop three times.

    MOV R0, #20H ;Address of addend 1, address of sum
    MOV R1, #30H ;Address of addend 2
    CLR C
    MOV R2, #3 ;Loop 3 times
A_LOOP:
    MOV A, @R0 ;Get
    ADDC A, @R1 ;Add
    MOV @R0, A ;Store
    INC R0
    INC R1
    DJNZ R2, A_LOOP
    CLR A
    ADDC A, #0 ;Get carry
    MOV 23H, A ;Save
    RET

;-----------------------------------------

Reference address：Write a 3-byte binary addition subroutine

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