73 lines
2.9 KiB
HTML
73 lines
2.9 KiB
HTML
<html><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<html>
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<head>
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<title>80386 Programmer's Reference Manual -- Opcode IN</title>
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</head>
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<body>
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<b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="IMUL.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/IMUL.HTM"> IMUL Signed Multiply</a><br>
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<b>next:</b><a href="INC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/INC.HTM"> INC Increment by 1</a>
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<p>
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<hr>
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<p>
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<h1>IN -- Input from Port</h1>
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<pre>
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Opcode Instruction Clocks Description
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E4 ib IN AL,imm8 12,pm=6*/26** Input byte from immediate port
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into AL
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E5 ib IN AX,imm8 12,pm=6*/26** Input word from immediate port
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into AX
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E5 ib IN EAX,imm8 12,pm=6*/26** Input dword from immediate port
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into EAX
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EC IN AL,DX 13,pm=7*/27** Input byte from port DX into AL
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ED IN AX,DX 13,pm=7*/27** Input word from port DX into AX
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ED IN EAX,DX 13,pm=7*/27** Input dword from port DX into
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EAX
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</pre>
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<em>
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<h3>Notes</h3>
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<pre>
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*If CPL <= IOPL
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**If CPL > IOPL or if in virtual 8086 mode
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</pre>
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</em>
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<h2>Operation</h2>
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<pre>
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IF (PE = 1) AND ((VM = 1) OR (CPL > IOPL))
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THEN (* Virtual 8086 mode, or protected mode with CPL > IOPL *)
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IF NOT I-O-Permission (SRC, width(SRC))
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THEN #GP(0);
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FI;
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FI;
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DEST := [SRC]; (* Reads from I/O address space *)
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</pre>
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<h2>Description</h2>
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IN transfers a data byte or data word from the port numbered by the second operand into the register (AL, AX, or EAX) specified by the first operand. Access any port from 0 to 65535 by placing the port number in the DX register and using an IN instruction with DX as the second parameter. These I/O instructions can be shortened by using an 8-bit port I/O in the instruction. The upper eight bits of the port address will be 0 when 8-bit port I/O is used.
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<h2>Flags Affected</h2>
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None
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<h2>Protected Mode Exceptions</h2>
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#GP(0) if the current privilege level is larger (has less privilege) than IOPL and any of the corresponding I/O permission bits in TSS equals 1
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<h2>Real Address Mode Exceptions</h2>
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None
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<h2>Virtual 8086 Mode Exceptions</h2>
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#GP(0) fault if any of the corresponding I/O permission bits in TSS equals 1
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<p>
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<hr>
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<p><b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="IMUL.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/IMUL.HTM"> IMUL Signed Multiply</a><br>
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<b>next:</b><a href="INC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/INC.HTM"> INC Increment by 1</a>
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</body>
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