RTI                    RTI Return from interrupt                      RTI

  Operation:  P from Stack, PC from Stack               N V - B D I Z C
                                                          From Stack

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  |  Implied/Stack |   RTI                 |   $40   |    1    |    6     |
  +----------------+-----------------------+---------+---------+----------+

What it does: Returns from an interrupt.

Major uses: None. You might want to add your own routines to your machine's normal interrupt routines (see SEI), but you won't be generating actual interrupts of your own. Consequently, you cannot ReTurn from Interrupts you never create.