"TMS320C55x DSP Library DSPLIB Programmer's Reference"

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ecip16recip1616-bit Reciprocal FunctionFunctionvoid recip16 (DATA *x, DATA *r, DATA *rexp, ushort nx)Argumentsx[nx]r[nx]rexp[nx]nxPointer to input data vector 1 of size nx.x[0]x[1]..x[nx–2]x[nx–1]Pointer to output data bufferr[0]r[1]..r[nx–2]r[nx–1]Pointer to exponent buffer for output values. Theseexponent values are in integer format.rexp[0]rexp[1]..rexp[nx–2]rexp[nx–1]Number of elements of input and output vectorsDescriptionThis routine returns the fractional and exponential portion of the reciprocal ofa Q15 number. Since the reciprocal is always greater than 1, it returns an exponentsuch that:r[i] * rexp[i] = true reciprocal in floating-pointAlgorithmYm 2*Ym Ym 2 * XnormIf we start with an initial estimate of Ym, the equation converges to a solutionvery rapidly (typically 3 iterations for 16-bit resolution).4-84
fftThe initial estimate can be obtained from a look-up table, from choosing a midpoint,or simply from linear interpolation. The method chosen for this problemis linear interpolation and is accomplished by taking the complement of theleast significant bits of the Xnorm value.Overflow Handling MethodologynoneSpecial Requirements noneImplementation Notes noneExampleBenchmarksSee examples/recip16 subdirectory(preliminary)Cycles † Core: 33 * nxOverhead: 12Code size(in bytes)69† 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).rfftFunctionForward Real FFT (in-place)void rfft (DATA *x, ushort nx, type);(reference cfft.asm and unpack.asm)Argumentsx [nx]nxPointer to input vector containing nx real elements. On output,vector x contains the first half (nx/2 complex elements) of theFFT output in the following order. Real FFT is a symmetricfunction around the Nyquist point, and for this reason only halfof the FFT(x) elements are required.On output x will contain the FFT(x) = y in the following format:y(0)Re y(nx/2)im → DC and Nyquisty(1)Re y(1)Imy(2)Re y(2)Im....y(nx/2)Re y(nx/2)ImComplex numbers are stored in Re-Im formatNumber of real elements in vector x. can take the followingvalues.nx = 16, 32, 64, 128, 256, 512, 1024Function Descriptions4-85
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TMS320C55x DSP LibraryProgrammer’
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PrefaceRead This FirstAbout This Ma
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Contentsatan16 . . . . . . . . . .
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DSP Routines1.1 DSP RoutinesThe TI
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DSPLIB Content / How to Install DSP
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Chapter 3Using DSPLIBThis chapter d
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Calling a DSPLIB Function from C3.2
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Calling a DSPLIB Function from Asse
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How DSPLIB Deals with Overflow and
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Chapter 4Function DescriptionsThis
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DSPLIB Functions4.2 DSPLIB Function
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DSPLIB FunctionsTable 4-2. Summary
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acorracorrFunctionArgumentsAutocorr
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addCycles †Code size(in bytes)Aub
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atan16Description This function cal
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expbexpFunctionBlock Exponent Imple
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cfftBenchmarks(preliminary)Cycles
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cfirCFFT - NOSCALEFFT Size Cycles
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cfirImplementation Notes The first
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cifftcifftFunctionInverse Complex F
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convolCIFFT - NOSCALEFFT Size Cycle
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convol1Figure 4-6. h Array in Memor
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convol2Figure 4-8. r Array in Memor
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convol2Figure 4-10. x Array in Memo
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dlmsImplementation NotesSpecial deb
Page 53 and 54: expnImplementation NotesDelayed ver
Page 55 and 56: firr[nx]Pointer to output vector of
Page 57 and 58: fir2Figure 4-14. x Array in Memoryo
Page 59 and 60: fir2Special Requirementsnh must be
Page 61 and 62: firdecr[nx/D]dbuffer[nh+1]nxnhDofla
Page 63 and 64: firinterpIoflagInterpolation factor
Page 65 and 66: firlatpbuffer [nh]nxnhoflagDelay bu
Page 67 and 68: firsnh2oflagHalf the number of coef
Page 69 and 70: fltoq15Figure 4-21. r Array in Memo
Page 71 and 72: hilb16dbuffer[nh + 2] Pointer to de
Page 73 and 74: iir32Figure 4-23. x Array in Memory
Page 75 and 76: iir32In the case of multiple-buffer
Page 77 and 78: iircas4nxoflagNumber of elements of
Page 79 and 80: iircas51This function retains the a
Page 81 and 82: iirlatBenchmarks(preliminary)Cycles
Page 83 and 84: ldiv16ldiv16Function32-bit by 16-bi
Page 85 and 86: log_10Special Requirements noneImpl
Page 87 and 88: lognThe coefficients Bi used in the
Page 89 and 90: maxidxmaxidxFunctionIndex of the Ma
Page 91 and 92: maxvecDescription Returns the maxim
Page 93 and 94: minvecminvalFunctionMinimum Value o
Page 95 and 96: mmulDescriptionAlgorithmThis functi
Page 97 and 98: negr[nx]Pointer to output data vect
Page 99 and 100: powernxoflagNumber of elements of i
Page 101 and 102: and16AlgorithmNot applicableOverflo
Page 103: and16initBenchmarksCycles Core: 13
Page 107 and 108: ifftrifftFunctionInverse Real FFT (
Page 109 and 110: sqrt_16DescriptionComputes the sine
Page 111 and 112: subr[nx]nxscaleoflagPointer to outp
Page 113 and 114: What DSPLIB Benchmarks are Provided
Page 115 and 116: DSPLIB Software Updates6.1 DSPLIB S
Page 117 and 118: Q3.12 Format / Q.15 Format / Q.31 F
Page 119 and 120: Calculating the Reciprocal of a Q15
Page 121 and 122: IndexIndex16-bit reciprocal functio
Page 123: Indexmmul 4-74mtrans 4-76mul32 4-76
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"TMS320C55x DSP Library DSPLIB Programmer's Reference"

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