PHX                     PHX Push Index X on Stack                      PHX

 65816 only!
                                                        N V M X D I C Z
  Operation:  X-Ws, S-2 -> S                            . . . . . . . .

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  | Implied        |   PHX                 |   $DA   |    1    |    3/4   |
  +----------------+-----------------------+---------+---------+----------+