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OUT
Outputs data from the accumulator register (AL, AX, or EAX) to a specified I/O port.
The following table covers the supported source and destinations.
| source | destination(s) |
|---|---|
| r8 | u8 (imm8 or r8) |
| r16 | u8 (imm8 or r8) |
| r32 | u8 (imm8 or r8) |
| #I | mN |
DO NOT support LOCK
The instruction is available in 64-bit mode, compatibility mode, and 32-bit/16-bit protected modes. The destination port must be specified by an 8-bit immediate or the DX register. If the destination port exceeds 255, the DX register SHALL be used.
The I/O privilege level (IOPL) in RFLAGS and the I/O permission bitmap in the TSS control access to the I/O ports. If the current privilege level (CPL) is greater than the IOPL and the port is not permitted in the bitmap, a General Protection Exception (#GP) SHALL occur.
The size of the data transferred is determined by the accumulator register used: AL for 1 byte, AX for word, and EAX for dword. Using a register other than the accumulator as the source is not supported.