"TMS320C55x DSP Library DSPLIB Programmer's Reference"

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dlmsnh Number of filter coefficients. Filter order = nh – 1.nh ≥ 3nxoflagLength of input and output data vectorsOverflow flag. If oflag = 1, a 32-bit overflow has occurred If oflag = 0, a 32-bit overflow has not occurredDescriptionAdaptive delayed least-mean-square (LMS) FIR filter using coefficients storedin vector h. Coefficients are updated after each sample based on the LMSalgorithm and using a constant step = 2*mu. The real data input is stored invector dbuffer. The filter output result is stored in vector r .LMS algorithm uses the previous error and the previous sample (delayed) totake advantage of the C55x LMS instruction.The delay buffer used is the same delay buffer used for other functions in theC55x DSP Library. There is one more data location in the circular delay bufferthan there are coefficients. Other C55x DSP Library functions use this delaybuffer to accommodate use of the dual-MAC architecture. In the DLMS function,we make use of the additional delay slot to allow coefficient updating aswell as FIR calculation without a need to update the circular buffer in the interimoperations.The FIR output calculation is based on x(i) through x(i–nh+1). The coefficientupdate for a delayed LMS is based on x(i–1) through x(i–nh). Therefore, byhaving a delay buffer of nh+1, we can perform all calculations with the givendelay buffer containing delay values of x(i) through x(i–nh). If the delay bufferwas of length nh, the oldest data sample, x(i–nh), would need to be updatedwith the newest data sample, x(i), sometime after the calculation of the first coefficientupdate term, but before the calculation of the last FIR term.AlgorithmFIR portionnh1r[j] h[k]* x[i k] 0 i nx 1k0Adaptation using the previous error and the previous sample:e(i) des(i 1) r (i 1)h k (i 1) h k (i) 2*mu * e(i 1) * x(i k 1)Overflow Handling MethodologyNo scaling implemented for overflow prevention.Special Requirements Minimum of 2 input and desired data samples. Minimum of 2 coefficients4-32
expnImplementation NotesDelayed version implemented to take advantage of the C55x LMS instruction.Effect of using delayed error signal on convergence minimum:For reference, following is the algorithm for the regular LMS (nondelayed):FIR portionnh1r[j] h[k]* x[i k] 0 i nx 1k0Adaptation using the current error and the current sample:e(i) des(i) r (i)h k (i 1) h k (i) 2*mu * e(i)*x(i k)ExampleBenchmarksSee examples/dlms subdirectory(preliminary)Cycles † Core: nx * (7 + 2*(nh – 1)) = nx * (5 + 2 * nh)Overhead: 26Code size(in bytes)122† 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).expnFunctionExponential Base eushort oflag = expn (DATA *x, DATA *r, ushort nx)(defined in expn.asm)Argumentsx[nx]r[nx]nxoflagPointer to input vector of size nx. x contains the numbersnormalized between (–1,1) in q15 formatPointer to output data vector (Q3.12 format) of size nx. r canbe equal to x.Length of input and output data vectorsOverflow flag. If oflag = 1, a 32-bit overflow has occurred If oflag = 0, a 32-bit overflow has not occurredFunction Descriptions4-33
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: dlmsImplementation NotesSpecial deb
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 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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