Bit Concat

Concatenates up to 128 input words into single output


HDL Coder / HDL Operations


The Bit Concat block concatenates up to 128 input words into a single output. The input port labeled L designates the lowest-order input word. The port labeled H designates the highest-order input word. The right-to-left ordering of words in the output follows the low-to-high ordering of input signals.

How the block operates depends on the number and dimensions of the inputs, as follows:

  • Single input: The input is a scalar or a vector. When the input is a vector, the coder concatenates the individual vector elements.

  • Two inputs: Inputs are any combination of scalar and vector. When one input is scalar and the other is a vector, the coder performs scalar expansion. Each vector element is concatenated with the scalar, and the output has the same dimension as the vector. When both inputs are vectors, they must have the same size.

  • Three or more inputs (up to a maximum of 128 inputs): Inputs are uniformly scalar or vector. All vector inputs must have the same size.


Number of Inputs: Enter an integer specifying the number of input signals. The number of block input ports updates when you change Number of Inputs.

  • Default: 2

  • Minimum: 1

  • Maximum: 128


Make sure that the Number of Inputs is equal to the number of signals you connect to the block. If the block has unconnected inputs, an error occurs at code generation time.


The block has up to 128 input ports, with H representing the highest-order input word, and L representing the lowest-order input word. The maximum concatenated output word size is 128 bits.

Supported Data Types

  • Input: Fixed-point, integer (signed or unsigned), Boolean

  • Output: Unsigned fixed-point or integer

Introduced in R2014a