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Справка Scilab >> Xcos > palettes > Integer palette > EXTRACTBITS

EXTRACTBITS

Bits Extraction

Block Screenshot

Description

For an integer input this block outputs a contiguous selection of bits. The operation can be summarized by this expression:

i.e. a bitwise AND between Input and Mask an integer of the same length as input with the bits to extract set to 1 and the other bits set to 0. Bits to Extract parameter defines the method by which the user selects the output bits as summarized by the following table with index 0, as that of the least significant bit :

Bits to Extract Output Number of Bits or Index of Bit
Upper Half Half of the input that contain the most significant bit Ignored
Lower Half Half of the input that contain the least significant bit Ignored
Range from MSB Number of Bits or Index of Bit bits of the input that contain the most significant bit (MSB) Number of bits to extract.
Range to LSB Number of Bits or Index of Bit bits of the input that contain the least significant bit (LSB) Number of bits to extract.
Range of bits Range of bits of the input between the indexes of the bits Start and End of Number of Bits or Index of Bit parameter. Vector with the format [Start, End] where start the first bit index and end the last bit index.

The output value depends also on the forth parameter Treat Bit Field as an Integer :

  • 0 : the output is directly the result of extraction.

  • 1 : the output is the integer conversion of the extraction result according to the signed or non-signed status of the input.

Data types

The block supports the following types :

  • Input : scalar. All Scilab's integer type (Data Type parameter).

  • Output : same type than input.

Dialog box

  • Data Type (3:int32, 4:int16, 5:int8, ...)

    It indicates the integer type on input: Between 3 and 8.

    Properties : Type 'vec' of size 1.

  • Bits to Extract

    It indicates the mode used to extract bits from the input data : Between 1 and 5 (1:Upper Half, 2:Lower Half, 3:Range from MSB, 4:Range to LSB, 5:Range of bits)

    Properties : Type 'vec' of size 1.

  • Number of Bits or Index of Bit

    When the Bits to Extract field is set to :

    • 1 or 2, this parameter is ignored.

    • 3 or 4, this parameter is used to determine the number of bits to extract. This number must be if the type is :

      • int32 or uint32: positive and less than 32.

      • int16 or uint16: positive and less than 16.

      • int8 or uint8: positive and less than 8.

    • 5, this parameter is used to determine range of bits to extract and it must have the [Start, End] form vector. Start must be less than End. These values must be, if the type is:

      • int32 or uint32: positive and less than 32.

      • int16 or uint16: positive and less than 16.

      • int8 or uint8: positive and less than 8.

    See description for more information

    Properties : Type 'vec' of size -1.

  • Treat Bit Field as an Integer (0:No, 1:Yes)

    0 or 1. It indicates the scaling mode to use on the output bits selection. See description for more explanation.

    Properties : Type 'vec' of size 1.

Default properties

  • always active: no

  • direct-feedthrough: yes

  • zero-crossing: no

  • mode: no

  • regular inputs:

    - port 1 : size [1,1] / type 3

  • regular outputs:

    - port 1 : size [1,1] / type 3

  • number/sizes of activation inputs: 0

  • number/sizes of activation outputs: 0

  • continuous-time state: no

  • discrete-time state: no

  • object discrete-time state: no

  • name of computational function: extract_bit_32_UH0

Example

In the following table, we present the results obtained for the number 215 according to several combinations of the parameters.

Input Bits to Extract Number of Bits or Index of Bit Treat Bit Field as an Integer Output
11010111 (215) Upper Half Ignored no 01100000 (208)
11010111 (215) Upper Half Ignored yes 00001101 (13)
11010111 (215) Lower Half Ignored no 00000111 (7)
11010111 (215) Lower Half Ignored yes 00000111 (7)
11010111 (215) Range starting with MSB 6 no 11010100 (212)
11010111 (215) Range starting with MSB 6 yes 00110101 (53)
11010111 (215) Range starting with LSB 6 no 00010111 (23)
11010111 (215) Range starting with LSB 6 yes 00010111 (23)
11010111 (215) Range of bits [ 2, 5 ] no 00010100 (20)
11010111 (215) Range of bits [ 2, 5 ] yes 00000101 (5)
11010111 (-41) Upper half Ignored no 11010000 (-48)
11010111 (-48) Upper half Ignored yes 11111101 (-3)

In the following diagram, two decimal digit numbers are coded on an only byte. The diagram decode the input to obtain two separate digits.

Interfacing function

  • SCI/modules/scicos_blocks/macros/IntegerOp/EXTRACTBITS.sci

Computational function

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_UH0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u32_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_LH.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_MSB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u32_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_LSB.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_RB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_32_RB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u32_RB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_UH0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u16_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_LH.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_MSB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u16_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_LSB.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_RB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_16_RB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u16_RB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_UH0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u8_UH1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_LH.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_MSB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u8_MSB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_LSB.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_RB0.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_8_RB1.c

  • SCI/modules/scicos_blocks/src/c/extract_bit_u8_RB1.c

See also

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Last updated:
Tue Feb 14 15:13:31 CET 2017