TXS              TXS Transfer index X to stack pointer                TXS
                                                        N Z C I D V
  Operation:  X -> S                                    . . . . . .
                                 (Ref: 8.8)
  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  |  Implied       |   TXS                 |   $9A   |    1    |    2     |
  +----------------+-----------------------+---------+---------+----------+