"TMS320C55x DSP Library DSPLIB Programmer's Reference"

cfftBenchmarks(preliminary)Cycles †Code size(in bytes)Core:2 * nx (off-place)4 * nx + 6 (in-place)Overhead: 1781 (includes support for both in-place and off-placebit-reverse)† Assumes all data is in on-chip dual-access RAM and that there is no bus conflict due to twiddletable reads and instruction fetches (provided linker command file reflects those conditions).cfftFunctionForward Complex FFTvoid cfft (DATA *x, ushort nx, type);(defined in cfft.asm)Argumentsx [2*nx]nxtypePointer to input vector containing nx complex elements(2*nx real elements) in bit-reversed order. On output, vectora contains the nx complex elements of the FFT(x). Complexnumbers are stored in interleaved Re-Im format.Number of complex elements in vector x. Must be between8 and 1024.FFT type selector. Types supported: If type = SCALE, scaled version selected If type = NOSCALE, non-scaled version selectedDescriptionAlgorithmComputes a complex nx-point FFT on vector x, which is in bit-reversed order.The original content of vector x is destroyed in the process. The nx complexelements of the result are stored in vector x in normal-order.(DFT)y[k] 1nx1(scale factor) * x[i]*cos 2* nx* i * k j sin 2* nx* i * ki0Overflow Handling MethodologyIf scale==1, scaling before each stage is implemented for overflowpreventionSpecial RequirementsThis function requires the inclusion of file “twiddle.inc” which contains thetwiddle table (automatically included).Function Descriptions4-15