Intel 64 and IA-32 Architectures Software Developers Manual Volume 2B, Instruction Set Reference, N-Z

Vol. 2B 4-19
INSTRUCTION SET REFERENCE, N-Z
Operation
IF ((PE = 1) and ((CPL > IOPL) or (VM = 1)))
THEN (* Protected mode with CPL > IOPL or virtual-8086 mode *)
IF (Any I/O Permission Bit for I/O port being accessed
= 1)
THEN (* I/O operation is not allowed *)
#GP(0);
ELSE (* I/O operation is allowed *)
DEST ← SRC; (* Writes to I/O port *)
FI;
ELSE (Real Mode or Protected Mode or 64-Bit Mode with CPL ≤ IOPL *)
DEST ← SRC; (* Writes to I/O port *)
FI;
Byte transfer:
IF 64-bit mode
Then
IF 64-Bit Address Size
THEN
IF DF
= 0
THEN RSI ← RSI RSI + 1;
ELSE RSI ← RSI or – 1;
FI;
ELSE (* 32-Bit Address Size *)
IF DF
= 0
THEN ESI ← ESI + 1;
ELSE ESI ← ESI – 1;
FI;
FI;
ELSE
IF DF
= 0
THEN (E)SI ← (E)SI + 1;
ELSE (E)SI ← (E)SI – 1;
FI;
FI;
Word transfer:
IF 64-bit mode
Then
IF 64-Bit Address Size
THEN
IF DF
= 0
THEN RSI ← RSI RSI + 2;
ELSE RSI ← RSI or – 2;
FI;