IRET Return from Interrupt

Flags affected:

        O D I T S Z A P C  OF: Overflow flag  TF: Trap flag AF: Aux carry
        F F F F F F F F F  DF: Direction flag SF: Sign flag PF: Parity flag
        * * * * * * * * *  IF: Interrupt flag ZF: Zero flag CF: Carry flag

Legal forms:

        IRET

Examples:

        IRET

Notes:

IRET must be used to exit from interrupt service routines called through INT or through interrupt hardware such as serial ports and the like. IRET pops the return address from the top of the stack into CS and IP, and then pops the next word from the stack into the Flags register. All flags are affected.

If the interrupt was triggered by hardware, there may be additional steps to be taken to prepare the hardware for another interrupt before IRET is executed. Consult your hardware documentation.

When using NASM, the actual opcode generated for IRET depends on the setting of the BITS setting, and governs whether a 16-bit return or 32-bit return is generated.

        r8 = AL AH BL BH CL CH DL DH        r16 = AX BX CX DX BP SP SI DI
        sr = CS DS SS ES FS GS              r32 = EAX EBX ECX EDX EBP ESP ESI EDI
        m8 = 8-bit memory data              m16 = 16-bit memory data
        m32 = 32-bit memory data            i8 = 8-bit immediate data
        i16 = 16-bit immediate data         i32 = 32-bit immediate data
        d8 = 8-bit signed displacement      d16 = 16-bit signed displacement
        d32 = 32-bit unsigned displacement