OUT

This instruction writes a byte to I/O memory. The flags are not affected.

Usage

OUT dest, source

dest refers to the I/O port or memory address. It can be an 8-bit immediate value (see operand types) or the DX register. If DX is used, the word stored in the register will be used as the I/O memory address.

source can be AL or AX. If it is AX, the value in AL will be written to the port specified by dest, and then the value in AH will be written to the next port.

Encoding

• Fixed port
  0101010w, port
• Variable port
  0101011w

Where w is the input size bit. w=0 indicates writing from AL and w=1 from AX.