OUT -- Output to Port

OUT -- Output to Port Opcode Instruction Clocks Description E6 ib OUT imm8,AL 10,pm=4*/24** Output byte AL to immediate port number E7 ib OUT imm8,AX 10,pm=4*/24** Output word AL to immediate port number E7 ib OUT imm8,EAX 10,pm=4*/24** Output dword AL to immediate port number EE OUT DX,AL 11,pm=5*/25** Output byte AL to port number in DX EF OUT DX,AX 11,pm=5*/25** Output word AL to port number in DX EF OUT DX,EAX 11,pm=5*/25** Output dword AL to port number in DX --------------------------------------------------------------------------- NOTES: *If CPL <= IOPL **If CPL > IOPL or if in virtual 8086 mode --------------------------------------------------------------------------- Operation IF (PE = 1) AND ((VM = 1) OR (CPL > IOPL)) THEN (* Virtual 8086 mode, or protected mode with CPL > IOPL *) IF NOT I-O-Permission (DEST, width(DEST)) THEN #GP(0); FI; FI; [DEST] = SRC; (* I/O address space used *) Description OUT transfers a data byte or data word from the register (AL, AX, or EAX) given as the second operand to the output port numbered by the first operand. Output to any port from 0 to 65535 is performed by placing the port number in the DX register and then using an OUT instruction with DX as the first operand. If the instruction contains an eight-bit port ID, that value is zero-extended to 16 bits. Flags Affected None Protected Mode Exceptions #GP(0) if the current privilege level is higher (has less privilege) than IOPL and any of the corresponding I/O permission bits in TSS equals 1 Real Address Mode Exceptions None Virtual 8086 Mode Exceptions #GP(0) fault if any of the corresponding I/O permission bits in TSS equals 1