amula10:
        mov     r2, #4          ;4 byte value
_amu1:
                   ;digit to add in acc
        xch     a, @r0
        mov     b, #10
        mul     ab              ;* 10
        add     a, @r0           ;add digit or carry
        mov     @r0, a
        clr     a
        addc    a, b            ;add carry
        inc     r0              ;next byte
        djnz    r2, _amu1
        ret