A.5.121 INSB, INSW, INSD: Input String from I/O Port
INSB ; 6C [186]
INSW ; o16 6D [186]
INSD ; o32 6D [386]
INSB inputs a byte from the I/O port specified in DX and stores it at
[ES:DI] or [ES:EDI]. It then increments or decrements (depending on the
direction flag: increments if the flag is clear, decrements if it is
set) DI or EDI.
The register used is DI if the address size is 16 bits, and EDI if it
is 32 bits. If you need to use an address size not equal to the current
BITS setting, you can use an explicit "a16" or "a32" prefix.
Segment override prefixes have no effect for this instruction: the use
of ES for the load from [DI] or [EDI] cannot be overridden.
INSW and INSD work in the same way, but they input a word or a
doubleword instead of a byte, and increment or decrement the addressing
register by 2 or 4 instead of 1.
The REP prefix may be used to repeat the instruction CX (or ECX - again,
the address size chooses which) times. The REP alias REPE, as well as
the differently-encoded REPNE, are both allowed as well. They behave in
the same way as REP.
See also OUTSB, OUTSW and OUTSD (section A.5.195).