"TMS320C55x DSP Library DSPLIB Programmer's Reference"

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firdecFigure 4–17. x Array in Memoryoldest x( ) entrynewest x( ) entryx(0)x(1)•x(nx–2)x(nx–1)lowest memory addresshighest memory addressFigure 4–18. r Array in Memoryoldest x( ) entrynewest x( ) entryr(0)r(1)•r(nx–2)r(nx–1)lowest memory addresshighest memory addressExampleBenchmarksSee examples/fir2 subdirectory(preliminary)Cycles † Core: (nx/2) * [5+(nh–3)]Overhead: 32Code size(in bytes)134† 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).firdecFunctionDecimating FIR Filterushort oflag = firdec (DATA *x, DATA *h, DATA *r, DATA *dbuffer , ushort nh,ushort nx, ushort D)(defined in decimate.asm)Argumentsx [nx]h[nh]Pointer to real input vector of nx real elements.Pointer to coefficient vector of size nh in normal order:H = b0 b1 b2 b3 …4-40
firdecr[nx/D]dbuffer[nh+1]nxnhDoflagPointer to real input vector of nx/D real elements.In-place computation (r = x) is allowedDelay buffer In the case of multiple-buffering schemes, this arrayshould be initialized to 0 for the first block only. Betweenconsecutive blocks, the delay buffer preservesprevious delayed input samples. It also preserves aptr to the next new entry into the dbuffer. This ptr ispreserved across function calls in dbuffer[0].Memory alignment: this is a circular buffer and muststart in a k-bit boundary(that is, the k LSBs of the startingaddress must be zeros) where k = log2 (nh).Number of real elements in vector xNumber of coefficientsDecimation factor. For example a D = 2 means you dropevery other sample. Ideally, nx should be a multiple ofD. If not, the trailing samples will be lost in the process.Overflow error flag If oflag = 1, a 32-bit data overflow occurred in an intermediateor final result.If oflag = 0, a 32-bit overflow has not occurred.DescriptionComputes a decimating real FIR filter (direct-form) using coefficient stored invector h. The real data input is stored in vector x. The filter output result isstored in vector r. This function retains the address of the delay filter memoryd containing the previous delayed values to allow consecutive processing ofblocks. This function can be used for both block-by-block and sample-bysamplefiltering (nx = 1).Algorithmr[j] nhk0h[k]x[j * D k]0 j nxOverflow Handling MethodologyNo scaling implemented for overflow prevention.Special Requirements noneImplementation Notes noneExampleSee examples/decim subdirectoryFunction Descriptions4-41
Page 1 and 2:
TMS320C55x DSP LibraryProgrammer’
Page 3 and 4:
PrefaceRead This FirstAbout This Ma
Page 5:
Contentsatan16 . . . . . . . . . .
Page 9 and 10: DSP Routines1.1 DSP RoutinesThe TI
Page 11 and 12: DSPLIB Content / How to Install DSP
Page 13 and 14: Chapter 3Using DSPLIBThis chapter d
Page 15 and 16: Calling a DSPLIB Function from C3.2
Page 17 and 18: Calling a DSPLIB Function from Asse
Page 19 and 20: How DSPLIB Deals with Overflow and
Page 21 and 22: Chapter 4Function DescriptionsThis
Page 23 and 24: DSPLIB Functions4.2 DSPLIB Function
Page 25 and 26: DSPLIB FunctionsTable 4-2. Summary
Page 27 and 28: acorracorrFunctionArgumentsAutocorr
Page 29 and 30: addCycles †Code size(in bytes)Aub
Page 31 and 32: atan16Description This function cal
Page 33 and 34: expbexpFunctionBlock Exponent Imple
Page 35 and 36: cfftBenchmarks(preliminary)Cycles
Page 37 and 38: cfirCFFT - NOSCALEFFT Size Cycles
Page 39 and 40: cfirImplementation Notes The first
Page 41 and 42: cifftcifftFunctionInverse Complex F
Page 43 and 44: convolCIFFT - NOSCALEFFT Size Cycle
Page 45 and 46: convol1Figure 4-6. h Array in Memor
Page 47 and 48: convol2Figure 4-8. r Array in Memor
Page 49 and 50: convol2Figure 4-10. x Array in Memo
Page 51 and 52: 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: fir2Special Requirementsnh must be
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 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 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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