STZ                      STZ Store zero in memory                     STZ

 65816 only!
                                                        N V M X D I Z C
  Operation:  0 -> M                                    . . . . . . . .

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  | Absolute       |   STZ $FFFF           |   $9C   |    3    |    4     |
  | Absolute,X     |   STZ $FFFF,X         |   $9E   |    3    |    5     |
  | Direct Page    |   STZ $FF             |   $64   |    2    |    3     |
  | Direct Page,X  |   STZ $FF,X           |   $74   |    2    |    4     |
  +----------------+-----------------------+---------+---------+----------+
  For penalty cycles on the 65816, check the desired addressing mode.