33. Bit Field Unsigned EXTract

33.1. Name

BFEXTU -- Bit field unsigned extract"

33.2. Synopsis

        BFEXTU        <ea>{OFFSET:WIDTH},Dn        (68020+)

        No size specs.

33.3. Function

<ea> indicates source operand which a part of bits have to be extracted and extended. Offset enables to locate first bit of field; width specifies number of bits of this field. Field is extracted, and extended to 32 bits by zero. Result is stored in the data register Dn. Be careful, this instruction operates from MSB to LSB!!

33.4. Format

                                                          <ea>
        ----------------------------------------=========================
        |15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
        |---|---|---|---|---|---|---|---|---|---|-----------|-----------|
        | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 |    MODE   | REGISTER  |
        |---|-----------|---|-------------------|-----------------------|
        | 0 |  REGISTER |Do |       OFFSET      |Dw |      WIDTH        |
        -----------------------------------------------------------------

        If Do = 0->Field "OFFSET" contains an immediate value which represents
        effective offset, value from 0 to 31.
        If Do = 1->Field "OFFSET" indicates number of a data register (bits 9
        and 10 of field cleared) which contains effective offset. Signed value
        is represented on 32 bits., so it's extended from -2 EXP 31 to
        (+2 EXP 31) -1.

        If Dw = 0->field "WIDTH" contains an immediate value between 1 and 31
        which indicates a width from 1 to 31 bits. A value of 0 indicates a
        width of 32 bits.
        If Dw = 1->field "WIDTH" indicates number of a data register (bits 3
        and 4 of field cleared) which contains width of bit field. The value
        modulo 32 can go from 1 to 31, indicating a width from 1 to 31 bits.
        A value 0 indicates a width of 32 bits.

REGISTER
        <ea> specifies destination, addressing modes are the followings:
        --------------------------------- -------------------------------
        |Addressing Mode|Mode| Register | |Addressing Mode|Mode|Register|
        |-------------------------------| |-----------------------------|
        |      Dn       |000 |No reg. Dn| |   (Abs).W     |111 |  000   |
        |-------------------------------| |-----------------------------|
        |      An       | -  |     -    | |   (Abs).L     |111 |  001   |
        |-------------------------------| |-----------------------------|
        |     (An)      |010 |No reg. An| |   (d16,PC)    |111 |  010   |
        |-------------------------------| |-----------------------------|
        |     (An)+     | -  |     -    | |   (d8,PC,Xi)  |111 |  011   |
        |-------------------------------| |-----------------------------|
        |    -(An)      | -  |     -    | |   (bd,PC,Xi)  |111 |  011   |
        |-------------------------------| |-----------------------------|
        |    (d16,An)   |101 |No reg. An| |([bd,PC,Xi],od)|111 |  011   | 
        |-------------------------------| |-----------------------------|
        |   (d8,An,Xi)  |110 |No reg. An| |([bd,PC],Xi,od)|111 |  011   |
        |-------------------------------| |-----------------------------|
        |   (bd,An,Xi)  |110 |No reg. An| |    #data      | -  |   -    |
        |-------------------------------| -------------------------------
        |([bd,An,Xi],od)|110 |No reg. An|
        |-------------------------------|
        |([bd,An],Xi,od)|110 |No reg. An|
        ---------------------------------

33.5. Result

        X - not affected
        N - Set if MSB of field is set. Cleared otherwise.
        Z - Set if all the bits of the field tested are zero.
            Cleared otherwise.
        V - Always cleared.
        C - Always cleared.

33.6. See also

BFEXTS