IN

IN - Input Byte or Word From Port

A byte, word or dword is read from “port” and placed in AL, AX or EAX respectively. If the port number is in the range of 0-255 it can be specified as an immediate, otherwise the port number must be specified in DX. Valid port ranges on the PC are 0-1024, though values through 65535 may be specified and recognized by third party vendors and PS/2's.

Usage:

	IN	accum,port	;

Modifies flags:

none

	Clocks				Size
Operands	808x	286	386	486	Bytes
accum,immed8	10/14	5	12	14	2
accum,immed8 (PM)	-	-	6/26	8/28/27	2
accum,DX	8/12	5	13	14	1
accum,DX (PM)	-	-	7/27	8/28/27	1

386+ protected mode timings depend on privilege levels.

first number is the timing if:	CPL ¾ IOPL
second number is the timing if:	CPL > IOPL or in VM 86 mode (386)
second number is the timing if:	CPL ‗ IOPL (486)
third number is the timing when:	virtual mode on 486 processor

486 virtual mode always requires 27 cycles

see Instructions list, Instruction Timing, 8086 Architecture, CPU

2023/01/05 22:53 · frater

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IN

IN - Input Byte or Word From Port

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