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Vol. 2A 3-85
INSTRUCTION SET REFERENCE, A-M
BTS—Bit Test and Set
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.
Operation
CF ← Bit(BitBase, BitOffset);
Bit(BitBase, BitOffset) ← 1;
Flags Affected
The CF flag contains the value of the selected bit before it is set. The OF, SF, ZF, AF,
and PF flags are undefined.
Protected Mode Exceptions
#GP(0) If the destination operand points to a non-writable segment.
If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
If the DS, ES, FS, or GS register contains a NULL segment
selector.
#SS(0) If a memory operand effective address is outside the SS
segment limit.
#PF(fault-code) If a page fault occurs.
#AC(0) If alignment checking is enabled and an unaligned memory
reference is made while the current privilege level is 3.
#UD If the LOCK prefix is used but the destination is not a memory
operand.
Real-Address Mode Exceptions
#GP If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
#SS If a memory operand effective address is outside the SS
segment limit.
#UD If the LOCK prefix is used but the destination is not a memory
operand.
Virtual-8086 Mode Exceptions
#GP If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
#SS If a memory operand effective address is outside the SS
segment limit.
#PF(fault-code) If a page fault occurs.