"TMS320C55x DSP Library DSPLIB Programmer's Reference"

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Calculating the Reciprocal of a Q15 NumberIf after each calculation we equate Ym(old) to Ym(new):Ym(old) Ym(new) YmThen equation (c8) evaluates to:Ym 2*Ym Ym 2 * Xnorm(c9)If we start with an initial estimate of Ym, then equation (c9) converges to a solutionvery rapidly (typically 3 iterations for 16-bit resolution).The 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 accomplished by taking the complement of the leastsignificant bits of the Xnorm value.Calculating the Reciprocal of a Q15 NumberB-3
IndexIndex16-bit reciprocal function 4-8432-bit by 16-bit long division function 4-6332-bit vector multiplication 4-76Aacorr 4-7adaptive delayed LMS filter 4-31add 4-9arctangent 2 implementation 4-10arctangent implementation 4-11atan16 4-11atan2_16 4-10autocorrelation 4-7Bbase 10 logarithm 4-64base 2 logarithm 4-66base e logarithm 4-67bexp 4-13block exponent implementation 4-13block FIR filter (fast) 4-37Ccascaded IIR direct form I 4-59cascaded IIR direct form II 4-56, 4-58cbrev 4-14cfft 4-15cfir 4-17cifft 4-21complex bit reverse 4-14complex FIR filter 4-17conversionfloating-point to Q15 (fltoq15) 4-49Q15 to floating-point (q15tofl) 4-80convol 4-23convol1 4-25convol2 4-27convolution 4-23convolution (fast) 4-25convolution (fastest) 4-27corr 4-30correlationauto (acorr) 4-7full-length (corr) 4-30correlation (full-length) 4-30Ddecimating FIR filter 4-40dlms 4-31double-precision IIR filter 4-53<strong>DSP</strong>LIBarguments 3-2calling a function from assembly language sourcecode 3-5calling a function from C 3-3content 2-2data types 3-2dealing with overflow and scaling issues 3-6how to install 2-2how to rebuild 2-3Eexpn 4-33exponential base e 4-33Index-1
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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
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expnImplementation NotesDelayed ver
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firr[nx]Pointer to output vector of
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fir2Figure 4-14. x Array in Memoryo
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fir2Special Requirementsnh must be
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firdecr[nx/D]dbuffer[nh+1]nxnhDofla
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firinterpIoflagInterpolation factor
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firlatpbuffer [nh]nxnhoflagDelay bu
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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 and 104: and16initBenchmarksCycles Core: 13
Page 105 and 106: fftThe initial estimate can be obta
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: Calculating the Reciprocal of a Q15
Page 123: Indexmmul 4-74mtrans 4-76mul32 4-76
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