From Nesdev wiki
The following code divide two 8-bit integers (range 0...255) and outputs a 16-bit result in fixed point 8.8 format. It is only using real calculations, no lookup table, thus the size of the code is very small.
;8-bit divide ;by Bregalad ;Enter with A = Dividend, Y=Divisor ;Output with YX = (A/Y) << 8, A = remainder Division sta Dvd ;Stores dividend sty Dvs ;Stores divisor ldy #$00 sty ResHi ;Clear result, setting up a ring counter iny ;by initializing the result to $0001. sty Res ;When the 1 gets shifted out, we're done ldy #$10 ;The loop is for 16-bit result - asl Dvd rol A ;Shift divisor in 1 bit bcs + ;If carry is set, the dividend is already greater cmp Dvs ;Check if fractional dividend is greater than divisor bcc ++ + sbc Dvs ;Subtract (C is always set) ++ rol Res ;Shift result (1 if subtraction was done, 0 otherwise) rol ResHi bcc - ldx Res ldy ResHi rts