||Return From Interrupt
Description: RETI is used to return from an interrupt service routine. RETI first enables interrupts of equal and lower priorities to the interrupt that is terminating. Program execution continues at the address that is calculated by popping the topmost 2 bytes off the stack. The most-significant-byte is popped off the stack first, followed by the least-significant-byte.
RETI functions identically to RET if it is executed outside of an interrupt service routine.
RET, Instruction Set