8051 Assembly Address Based 16 bit Subtraction program with Carry

    ORG 0000H

    CLR C

    MOV R1, #00H

                MOV DPTR, #0030H

                MOVX A, @DPTR

                MOV R0, A

                INC DPTR

                MOVX A, @DPTR

                SUBB A, R0

                JNC OVER1

                INC R1

                CPL A

                ADD A, #01H

                MOV DPTR, #0090H

                MOVX @DPTR, A

                MOV A, R1

                MOV R7, A

OVER1:   MOV DPTR, #0090H

                MOVX @DPTR, A

                MOV A, R1

                MOV R7, A

                MOV DPTR, #0032H

                MOVX A, @DPTR

                MOV R2, A

                INC DPTR

                MOVX A, @DPTR

                MOV R3, A

                MOV A, R2

                ADD A, R7

                MOV R2, A

                MOV A, R3

                SUBB A, R2

                JNC OVER2

                INC R4

                CPL A

                MOV A, #01H

                MOV DPTR, #0091H

                MOVX @DPTR, A

                MOV A, R4

                INC DPTR

                MOVX @DPTR, A

OVER2:   MOV DPTR, #0091H

                MOVX @DPTR, A

                MOV A, R4

                INC DPTR

                MOVX @DPTR, A

                MOV PCON, #02H