.macro div2_16bit(address) {
  ldy address + 1
  bpl ok
  inc address +0
  bne ok
  iny
ok:
  cpy #$80
  tya
  ror
  ror address + 0
  sta address + 1
}

.Div16_2
  LDA address
  AND address+1
  INC A    ; turns 0xFFFF into zero, anything else will be non-zero
  BNE Shift16
  STA address    ; explicitly store a zero result
  STA address+1
  BEQ End
.Shift16
  LDA address+1
  ASL A
  ROR address+1
  ROR address
.End