ia-32_instruction-set-ref_a-m

Data and limits operation cf bitbitbase bitoffset

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Unformatted text preview: the CS, DS, ES, FS, or GS segment limit. If a memory operand effective address is outside the SS segment limit. If a page fault occurs. If alignment checking is enabled and an unaligned memory reference is made. Compatibility Mode Exceptions Same exceptions as in Protected Mode. Vol. 2 3-81 INSTRUCTION SET REFERENCE, A-M 64-Bit Mode Exceptions #SS(0) #GP(0) #PF(fault-code) #AC(0) If a memory address referencing the SS segment is in a noncanonical form. If the memory address is in a non-canonical form. If a page fault occurs. If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3. 3-82 Vol. 2 INSTRUCTION SET REFERENCE, A-M BTS--Bit Test and Set Opcode 0F AB 0F AB REX.W + 0F AB 0F BA /5 ib 0F BA /5 ib REX.W + 0F BA /5 ib Instruction BTS r/m16, r16 BTS r/m32, r32 BTS r/m64, r64 BTS r/m16, imm8 BTS r/m32, imm8 BTS r/m64, imm8 64-Bit Mode Valid Valid Valid Valid Valid Valid Compat/ Leg Mode Valid Valid N.E. Valid Valid N.E. Description Store selected bit in CF flag and set. Store selected bit in CF flag and set. Store selected bit in CF flag and set. Store selected bit in CF flag and set. Store selected bit in CF flag and set. Store selected bit in CF flag and set. Description Selects the bit in a bit string (specified with the first operand, called the bit base) at the bit-position designated by the bit offset operand (second operand), stores the value of the bit in the CF flag, and sets the selected bit in the bit string to 1. The bit base operand can be a register or a memory location; the bit offset operand can be a register or an immediate value: If the bit base operand specifies a register, the instruction takes the modulo 16, 32, or 64 of the bit offset operand (modulo size depends on the mode and register size; 64-bit operands are available only in 64-bit mode). This allows any bit position to be selected. If the bit base operand specifies a memory location, the operand represents the address of the byte in memory that contains the bit base (bit 0 of the specified byte) of the bit string. The range of the bit position that can be referenced by the offset operand depends on the operand size. See also: Bit(BitBase, BitOffset) on page 3-10. Some assemblers support immediate bit offsets larger than 31 by using the immediate bit offset field in combination with the displacement field of the memory operand. See "BT--Bit Test" in this chapter for more information on this addressing mechanism. This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically. In 64-bit mode, the instruction's default operation size is 32 bits. Using a REX prefix in the form of REX.R permits access to additional registers (R8-R15). Using a REX prefix in the form of REX.W promotes operation to 64 bits. See the summary chart at the beginning of this section for encoding data and limits. Vol. 2 3-83 INSTRUCTION SET REFERENCE, A-M Operation CF Bit(BitBase, BitOffset); Bit(B...
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This note was uploaded on 10/01/2013 for the course CPE 103 taught by Professor Watlins during the Winter '11 term at Mississippi State.

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