TXA                TXA Transfer index X to accumulator                TXA

  Operation:  X -> A                                    N V - B D I Z C
                                                        / . . . . . / .

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  |  Implied       |   TXA                 |   $8A   |    1    |    2     |
  +----------------+-----------------------+---------+---------+----------+