70 lines
3.5 KiB
HTML
70 lines
3.5 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 SUB</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="STR.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STR.HTM"> STR Store Task Register</a><br>
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<b>next:</b><a href="TEST.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/TEST.HTM"> TEST Logical Compare</a>
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<p>
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<hr>
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<p>
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<h1>SUB -- Integer Subtraction</h1>
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<pre>
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Opcode Instruction Clocks Description
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2C ib SUB AL,imm8 2 Subtract immediate byte from AL
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2D iw SUB AX,imm16 2 Subtract immediate word from AX
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2D id SUB EAX,imm32 2 Subtract immediate dword from EAX
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80 /5 ib SUB r/m8,imm8 2/7 Subtract immediate byte from r/m byte
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81 /5 iw SUB r/m16,imm16 2/7 Subtract immediate word from r/m word
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81 /5 id SUB r/m32,imm32 2/7 Subtract immediate dword from r/m
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dword
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83 /5 ib SUB r/m16,imm8 2/7 Subtract sign-extended immediate byte
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from r/m word
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83 /5 ib SUB r/m32,imm8 2/7 Subtract sign-extended immediate byte
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from r/m dword
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28 /r SUB r/m8,r8 2/6 Subtract byte register from r/m byte
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29 /r SUB r/m16,r16 2/6 Subtract word register from r/m word
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29 /r SUB r/m32,r32 2/6 Subtract dword register from r/m
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dword
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2A /r SUB r8,r/m8 2/7 Subtract byte register from r/m byte
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2B /r SUB r16,r/m16 2/7 Subtract word register from r/m word
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2B /r SUB r32,r/m32 2/7 Subtract dword register from r/m
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dword
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</pre>
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<h2>Operation</h2>
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<pre>
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IF SRC is a byte and DEST is a word or dword
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THEN DEST := DEST - SignExtend(SRC);
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ELSE DEST := DEST - SRC;
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FI;
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</pre>
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<h2>Description</h2>
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SUB subtracts the second operand (SRC) from the first operand (DEST). The first operand is assigned the result of the subtraction, and the flags are set accordingly.
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<p>When an immediate byte value is subtracted from a word operand, the immediate value is first sign-extended to the size of the destination operand.
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<h2>Flags Affected</h2>
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OF, SF, ZF, AF, PF, and CF as described in <a href="APPC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/APPC.HTM">Appendix C</a>
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<h2>Protected Mode Exceptions</h2>
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#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
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<h2>Real Address Mode Exceptions</h2>
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Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH
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<h2>Virtual 8086 Mode Exceptions</h2>
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Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault
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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="STR.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STR.HTM"> STR Store Task Register</a><br>
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<b>next:</b><a href="TEST.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/TEST.HTM"> TEST Logical Compare</a>
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</body>
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