A 6502 instruction that sets the I (interrupt disable) flag, preventing IRQs from interrupting the code.
  • Function: 1 => I
  • Updates flags: . . . . . I . .
  • Opcode number: impl $78

Caution: Do not confuse this with the sti instruction of x86, which does the exact opposite.

As opposed to: CLI
See also: 6502 instructions | 6502 addressing modes