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80386 Programmer's Reference Manual -- Opcode XLAT |
XLAT/XLATB -- Table Look-up TranslationD7 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] OperationIF AddressSize = 16 THEN AL := (BX + ZeroExtend(AL)) ELSE (* AddressSize = 32 *) AL := (EBX + ZeroExtend(AL)); FI; DescriptionXLAT changes the AL register from the table index to the table entry. AL should be the unsigned index into a table addressed by DS:BX (for an address-size attribute of 16 bits) or DS:EBX (for an address-size attribute of 32 bits).The operand to XLAT allows for the possibility of a segment override. XLAT uses 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 previous instruction. The no-operand form, XLATB, can be used if the BX/EBX table will always reside in the DS segment. Flags AffectedNoneProtected Mode Exceptions#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 faultReal Address Mode ExceptionsInterrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFHVirtual 8086 Mode ExceptionsSame exceptions as in Real Address Mode; #PF(fault-code) for a page fault
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