BTR             Bit Test and Reset                   Flags: O D I T S Z A P C
                                                            - - - - - - - - *
BTR destination,source                               CPU: 386+

        Logic   CF ← bit, bit ← 0

    The source specifies a bit index in the destination operand.
    BTR copies that bit to the carry flag and then resets it in
    destination.


    Opcode      Format
    0F B3       BTR r/m16,r16
    0F B3       BTR r/m32,r32
    0F BA /6 ib BTR r/m16,imm8
    0F BA /6 ib BTR r/m32,imm8


    Length and timing
    Operands    Bytes   8088    186     286     386     486     Pentium
    reg, reg     3                               6       6       7   NP
    mem, reg   3+d(0,1,2,4)                     13      13      13   NP
    reg, imm8    3+i(1)                          6       6       7   NP
    mem, imm8  3+d(0,1,2,4)+i(1)                 8       8       8   NP