.DEF rd1l = R2 ; LSB 16-bit-number to be divided   делимое младший
.DEF rd1h = R1 ; MSB 16-bit-number to be divided   делимое старший
.DEF rd1u = R3 ; interim register
.DEF rd2  = R4 ; 8-bit-number to divide with        делитель
.DEF rel  = R6 ; LSB result                         результат младший
.DEF reh  = R5 ; MSB result                         результат старший
div16:
clr rd1u ; clear interim register
clr reh ; clear result (the result registers
clr rel ; are also used to count to 16 for the
inc rel ; division steps, is set to 1 at start)
div8a:
clc ; clear carry-bit
rol rd1l ; rotate the next-upper bit of the number
rol rd1h ; to the interim register (multiply by 2)
rol rd1u
brcs div8b ; a one has rolled left, so subtract
cp rd1u,rd2 ; Division result 1 or 0?
brcs div8c ; jump over subtraction, if smaller
div8b:
sub rd1u,rd2; subtract number to divide with
sec ; set carry-bit, result is a 1
rjmp div8d ; jump to shift of the result bit
div8c:
clc ; clear carry-bit, resulting bit is a 0
div8d:
rol rel ; rotate carry-bit into result registers
rol reh
brcc div8a ; as long as zero rotate out of the result
; registers: go on with the division loop
; End of the division reached
RET