DSP Builder for Intel® FPGAs (Advanced Blockset): Handbook

ID 683337
Date 4/01/2024
Document Table of Contents

14.4.8. Bit Combine (BitCombine)

The BitCombine block outputs the bit concatenation of the input values:

((h << bitwidth(i)) | i)

You can change the number of inputs on the BitCombine block according to your requirements. When Boolean vectors are input on multiple ports, DSP Builder combines corresponding components from each vector and outputs a vector of signals. The widths of all input vectors must match. However, the widths of the signals arriving on different inputs do not have to be equal. The one input BitCombine block is a special case that concatenates all the components of the input vector, so that one wide scalar signal is output. Use with logical operators to apply a 1-bit reducing operator to Boolean vectors.

If all inputs on all ports are complex signals, DSP Builder applies the bit combine operation to the real part and imaginary parts component by component. DSP Builder does not concatenate the real and imaginary parts.

If the inputs on multiple ports are a mixture of real and complex signals, DSP Builder converts the real values to complex values that have zero padded imaginary parts. DSP Builder then concatenates the imaginary parts of all inputs as before.

Table 169.  Parameters for the BitCombine Block
Parameter Description
Number of inputs Specifies the number of inputs.
Output data type mode Determines how the block sets its output data type:
  • Inherit via internal rule: the number of integer and fractional bits is the maximum of the number of bits in the input data types.
  • Specify via dialog: you can set the output type of the block explicitly using additional fields that are available when this option is selected.This option reinterprets the output bit pattern from the LSB up according to the specified type.
  • Boolean: the output type is Boolean.
Output data type Specifies the output data type. For example, sfix(16), uint(8).
Output scaling value Specifies the output scaling value. For example, 2^-15.
Table 170.  Port Interface for the BitCombine Block
Signal Direction Type Description Vector Data Support Complex Data Support
i Input Any fixed-point type Operand Yes Yes
h Input Any fixed-point type Operand Yes Yes
q Output Derived fixed-point type Result Yes Yes