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Embedded Coder/ Embedded Targets/ Processors/ Texas Instruments C6000/ Optimization/ C62x DSP Library
The Bit Reverse block bit-reverses the elements of each channel of a complex input signal, X. The Bit Reverse block is primarily used to provide ordered inputs and outputs to or from blocks that perform FFTs. Inputs to this block must be 16-bit fixed-point data types.
The Bit Reverse block supports discrete sample times and little-endian code generation only.
In simulation, the Bit Reverse block is equivalent to the TMS320C62x DSP Library assembly code function DSP_bitrev_cplx. During code generation, this block calls the DSP_bitrev_cplx routine to produce optimized code.
The Bit Reverse block reorders the output of the C62xRadix-2 FFT in the model below to natural order.
The following code calculates the same FFT in the workspace. The output from this calculation, y2, is displayed side-by-side with the output from the model, c. The outputs match, showing that the Bit Reverse block reorders the Radix-2 FFT output to natural order:
k = 4;
n = 2^k;
xr = zeros(n, 1);
xr(2) = 0.5;
xi = zeros(n, 1);
x2 = complex(xr, xi);
y2 = fft(x2);
[y2, c]
0.5000 0.5000
0.4619 - 0.1913i 0.4619 - 0.1913i
0.3536 - 0.3536i 0.3535 - 0.3535i
0.1913 - 0.4619i 0.1913 - 0.4619i
0 - 0.5000i 0 - 0.5000i
-0.1913 - 0.4619i -0.1913 - 0.4619i
-0.3536 - 0.3536i -0.3535 - 0.3535i
-0.4619 - 0.1913i -0.4619 - 0.1913i
-0.5000 -0.5000
-0.4619 + 0.1913i -0.4619 + 0.1913i
-0.3536 + 0.3536i -0.3535 + 0.3535i
-0.1913 + 0.4619i -0.1913 + 0.4619i
0 + 0.5000i 0 + 0.5000i
0.1913 + 0.4619i 0.1913 + 0.4619i
0.3536 + 0.3536i 0.3535 + 0.3535i
0.4619 + 0.1913i 0.4619 + 0.1913iC62xRadix-2 FFT, C62xRadix-2 IFFT
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