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OR.htm
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML>
<HEAD>
<TITLE>80386 Programmer's Reference Manual -- Opcode OR</TITLE>
</HEAD>
<BODY STYLE="width:80ch">
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="NOT.htm"> NOT One's Complement Negation</A><BR>
<B>next:</B><A HREF="OUT.htm"> OUT Output to Port</A>
<P>
<HR>
<P>
<H1>OR -- Logical Inclusive OR</H1>
<PRE>
Opcode Instruction Clocks Description
0C ib OR AL,imm8 2 OR immediate byte to AL
0D iw OR AX,imm16 2 OR immediate word to AX
0D id OR EAX,imm32 2 OR immediate dword to EAX
80 /1 ib OR r/m8,imm8 2/7 OR immediate byte to r/m byte
81 /1 iw OR r/m16,imm16 2/7 OR immediate word to r/m word
81 /1 id OR r/m32,imm32 2/7 OR immediate dword to r/m dword
83 /1 ib OR r/m16,imm8 2/7 OR sign-extended immediate byte
with r/m word
83 /1 ib OR r/m32,imm8 2/7 OR sign-extended immediate byte
with r/m dword
08 /r OR r/m8,r8 2/6 OR byte register to r/m byte
09 /r OR r/m16,r16 2/6 OR word register to r/m word
09 /r OR r/m32,r32 2/6 OR dword register to r/m dword
0A /r OR r8,r/m8 2/7 OR r/m byte to byte register
0B /r OR r16,r/m16 2/7 OR r/m word to word register
0B /r OR r32,r/m32 2/7 OR r/m dword to dword register
</PRE>
<H2>Operation</H2>
<PRE>
DEST := DEST OR SRC;
CF := 0;
OF := 0
</PRE>
<H2>Description</H2>
OR computes the inclusive OR of its two operands and places the result
in the first operand. Each bit of the result is 0 if both corresponding
bits of the operands are 0; otherwise, each bit is 1.
<H2>Flags Affected</H2>
OF := 0, CF := 0; SF, ZF, and PF as described in <A HREF="appc.htm">Appendix C</A>; AF is
undefined
<H2>Protected Mode Exceptions</H2>
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal
memory operand effective address in the CS, DS, ES, FS, or GS
segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)
for a page fault
<H2>Real Address Mode Exceptions</H2>
Interrupt 13 if any part of the operand would lie outside of the effective
address space from 0 to 0FFFFH
<H2>Virtual 8086 Mode Exceptions</H2>
Same exceptions as in real-address mode; #PF(fault-code) for a page
fault
<P>
<HR>
<P>
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="NOT.htm"> NOT One's Complement Negation</A><BR>
<B>next:</B><A HREF="OUT.htm"> OUT Output to Port</A>
</BODY>