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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode XLAT</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="XCHG.htm"> XCHG Exchange Register/Memory with Register</A><BR><B>next:</B><A HREF="XOR.htm"> XOR Logical Exclusive OR</A><P><HR><P><H1>XLAT/XLATB -- Table Look-up Translation</H1><PRE>D7 XLAT m8 5 Set AL to memory byte DS:[(E)BX + unsigned AL]D7 XLATB 5 Set AL to memory byte DS:[(E)BX + unsigned AL]</PRE><H2>Operation</H2><PRE>IF AddressSize = 16THEN AL := (BX + ZeroExtend(AL))ELSE (* AddressSize = 32 *) AL := (EBX + ZeroExtend(AL));FI;</PRE><H2>Description</H2>XLAT changes the AL register from the table index to the table entry. ALshould be the unsigned index into a table addressed by DS:BX (for anaddress-size attribute of 16 bits) or DS:EBX (for an address-size attributeof 32 bits).<P>The operand to XLAT allows for the possibility of a segment override. XLATuses the contents of BX even if they differ from the offset of the operand.The offset of the operand should have been moved intoBX/EBX with a previousinstruction.<P>The no-operand form, XLATB, can be used if the BX/EBX table will alwaysreside in the DS segment.<H2>Flags Affected</H2>None<H2>Protected Mode Exceptions</H2>#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 effectiveaddress 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="XCHG.htm"> XCHG Exchange Register/Memory with Register</A><BR><B>next:</B><A HREF="XOR.htm"> XOR Logical Exclusive OR</A></BODY>⌨️ 快捷键说明
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