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Conditions for Code Replacement of DSP Blocks with HVX

DSP blocks (you will require DSP Toolbox installed) that can be used with the Support Package for Qualcomm® Hexagon® processors require specific conditions to allow code replacement with the Hexagon Vector Extension (HVX). You use this code replacement when generating C/C++ code from a model. The support package do not support any multi-rate DSP blocks in the Code Replacement Library (CRL). The Hexagon Vector Extension (HVX) supports these DSP blocks only when you set specific properties, as indicated in the following table:

 DSP BlockInput RequirementsParameter RequirementsEquivalent Functions in Replacement
1Discrete FIR Filter

  • Real values.

  • single data type

  • Input frame length >= Filter length rounded to nearest multiple of 32

  • Filter structure: Direct Form.

  • Input processing: Columns as channels (frame based).

  • Coefficients source: Dialog parameters or Input port.

  • Filter length >=16

 
2FFT (DSP System Toolbox)

  • single data type.

  • Real values.

  • Input size must be in powers of 2.

  • Real : 64,128, ….

  • Complex: 32,64,...

  • FFT Length: same as input length (If Inherit FFT length from input dimensions: off)

  • FFT implementation: Auto

  • Divide output by FFT length: Off

  • Output in bit reversed order: off

  • Real FFT

    • mw_qhdsp_hvx_fft_gen_twiddles_real_acf

    • mw_qhdsp_hvx_r1dfft_af

  • Complex FFT

    • mw_qhdsp_hvx_fft_gen_twiddles_complex_acf

    • mw_qhdsp_hvx_c1dfft_af

3IFFT (DSP System Toolbox)

  • single data type.

  • Complex input values.

  • Input size must be in powers of 2.

  • Real : 64, 128 ….

  • Complex: 32, 64...

  • FFT Length: same as input length (If Inherit FFT length from input dimensions: off)

  • Input in bit reversed order: off

  • Real FFT

    • mw_qhdsp_fft_gen_twiddles_real_acf

    • mw_qhdsp_hvx_r1dfft_af

  • Complex FFT

    • mw_qhdsp_hvx_fft_gen_twiddles_complex_acf

    • mw_qhdsp_hvx_c1dfft_af

Note

Use only column-major layout for QHL/HVX replacements. For more information, see Row-Major and Column-Major Array Layouts.

See Also

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