mov r0, #027h ;divident high
mov r1, #015h; divident low
mov r2, #007h;divider high
mov r3, #0d0h; divider low
mov r5, #00h
mov r4, #00h
;3 0000 -2000
;  r0 r1
;: r2 r3
;________
; = r4 r5
sub_again:
        cjne r0, #0,start_sub
        cjne r1, #0, start_sub
        ljmp end
        start_sub:
                clr c
                mov a, r1
                subb a, r3
                mov r1, a
                jc ovf1
                cont1:
                        mov a,r0
                        subb a, r2
                        mov r0,a
                jnc inc_result
                ljmp end;
ovf1:
        clr c ; better safe than sorry
        dec r0
        ljmp cont1
inc_result:
        inc r5;
        cjne r5,#0h, sub_again
inc_result2dig:
        inc r4
        ljmp sub_again
end :ljmp end