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198 lines
15 KiB
198 lines
15 KiB
;* ======================================================================== *;
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;* TEXAS INSTRUMENTS, INC. *;
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;* *;
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;* DSPLIB DSP Signal Processing Library *;
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;* *;
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;* Release: Revision 1.04b *;
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;* CVS Revision: 1.6 Sun Sep 29 03:31:21 2002 (UTC) *;
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;* Snapshot date: 23-Oct-2003 *;
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;* *;
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;* This library contains proprietary intellectual property of Texas *;
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;* Instruments, Inc. The library and its source code are protected by *;
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;* various copyrights, and portions may also be protected by patents or *;
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;* other legal protections. *;
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;* *;
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;* This software is licensed for use with Texas Instruments TMS320 *;
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;* family DSPs. This license was provided to you prior to installing *;
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;* the software. You may review this license by consulting the file *;
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;* TI_license.PDF which accompanies the files in this library. *;
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;* ------------------------------------------------------------------------ *;
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;* Copyright (C) 2003 Texas Instruments, Incorporated. *;
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;* All Rights Reserved. *;
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;* ======================================================================== *;
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;* ======================================================================== *;
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;* Assembler compatibility shim for assembling 4.30 and later code on *;
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;* tools prior to 4.30. *;
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;* ======================================================================== *;
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;* ======================================================================== *;
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;* End of assembler compatibility shim. *;
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;* ======================================================================== *;
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* ========================================================================= *
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* TEXAS INSTRUMENTS, INC. *
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* *
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* NAME *
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* DSP_bitrev_cplx *
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* *
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* REVISION DATE *
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* 18-Sep-2001 *
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* *
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* USAGE *
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* This routine is C Callable and can be called as: *
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* *
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* void DSP_bitrev_cplx(int *x, short *index, int nx); *
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* *
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* x[nx] : Complex input array to be bit-reversed. One element *
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* consists of a pair of 16-bit data. *
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* index[]: Array of size ~sqrt(nx) created by the routine *
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* bitrev_index to allow the fast implementation of the *
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* bit-reversal. *
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* nx : Number of elements in array x[]. Must be power of 2. *
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* *
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* DESCRIPTION *
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* This routine performs the bit-reversal of the input array x[], *
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* where x[] is an integer array of length nx containing 16-bit *
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* complex pairs of data. This routine requires the index array *
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* provided by the program below. This index should be generated at *
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* compile time not by the DSP. *
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* *
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* authorizes the use of the bit-reversal code and related table *
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* generation code with TMS320-family DSPs manufactured by TI. *
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* *
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* /* ----------------------------------------------------------- */ *
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* /* This routine calculates the index for bit reversal of */ *
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* /* an array of length nx. The length of the index table is */ *
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* /* 2^(2*ceil(k/2)) where nx = 2^k. */ *
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* /* */ *
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* /* In other words, the length of the index table is: */ *
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* /* - for even power of radix: sqrt(nx) */ *
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* /* - for odd power of radix: sqrt(2*nx) */ *
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* /* ----------------------------------------------------------- */ *
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* void bitrev_index(short *index, int nx) *
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* { *
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* int i, j, k, radix = 2; *
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* short nbits, nbot, ntop, ndiff, n2, raddiv2; *
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* *
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* nbits = 0; *
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* i = nx; *
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* while (i > 1) *
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* { *
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* i = i >> 1; *
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* nbits++; *
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* } *
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* *
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* raddiv2 = radix >> 1; *
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* nbot = nbits >> raddiv2; *
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* nbot = nbot << raddiv2 - 1; *
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* ndiff = nbits & raddiv2; *
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* ntop = nbot + ndiff; *
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* n2 = 1 << ntop; *
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* *
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* index[0] = 0; *
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* for ( i = 1, j = n2/radix + 1; i < n2 - 1; i++) *
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* { *
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* index[i] = j - 1; *
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* *
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* for (k = n2/radix; k*(radix-1) < j; k /= radix) *
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* j -= k*(radix-1); *
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* *
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* j += k; *
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* } *
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* index[n2 - 1] = n2 - 1; *
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* } *
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* *
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* C CODE *
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* void bitrev(int *x, short *index, int nx) *
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* { *
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* int i; *
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* short i0, i1, i2, i3; *
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* short j0, j1, j2, j3; *
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* int xi0, xi1, xi2, xi3; *
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* int xj0, xj1, xj2, xj3; *
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* short t; *
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* int a, b, ia, ib, ibs; *
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* int mask; *
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* int nbits, nbot, ntop, ndiff, n2, halfn; *
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* short *xs = (short *) x; *
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* *
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* nbits = 0; *
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* i = nx; *
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* while (i > 1) *
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* { *
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* i = i >> 1; *
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* nbits++; *
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* } *
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* *
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* nbot = nbits >> 1; *
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* ndiff = nbits & 1; *
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* ntop = nbot + ndiff; *
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* n2 = 1 << ntop; *
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* mask = n2 - 1; *
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* halfn = nx >> 1; *
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* *
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* for (i0 = 0; i0 < halfn; i0 += 2) *
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* { *
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* b = i0 & mask; *
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* a = i0 >> nbot; *
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* if (!b) ia = index[a]; *
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* ib = index[b]; *
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* ibs = ib << nbot; *
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* *
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* j0 = ibs + ia; *
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* t = i0 < j0; *
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* xi0 = x[i0]; *
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* xj0 = x[j0]; *
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* *
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* if (t){x[i0] = xj0; *
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* x[j0] = xi0;} *
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* *
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* i1 = i0 + 1; *
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* j1 = j0 + halfn; *
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* xi1 = x[i1]; *
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* xj1 = x[j1]; *
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* x[i1] = xj1; *
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* x[j1] = xi1; *
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* *
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* i3 = i1 + halfn; *
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* j3 = j1 + 1; *
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* xi3 = x[i3]; *
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* xj3 = x[j3]; *
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* if (t){x[i3] = xj3; *
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* x[j3] = xi3;} *
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* } *
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* } *
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* *
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* ASSUMPTIONS *
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* nx must be a power of 2. *
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* The table from bitrev_index is already created. *
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* LITTLE ENDIAN configuration used. *
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* *
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* NOTES *
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* If nx <= 4K one can use the char (8-bit) data type for *
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* the "index" variable. This would require changing the LDH when *
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* loading index values in the assembly routine to LDB. This would *
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* further reduce the size of the Index Table by half its size. *
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* *
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* This code is interrupt tolerant, but not interruptible. *
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* *
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* CYCLES *
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* (nx/4 + 2) * 7 + 18 *
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* *
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* e.g. nx = 256, cycles = 480 *
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* *
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* CODESIZE *
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* 352 bytes *
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* *
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* *
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* ------------------------------------------------------------------------- *
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* Copyright (c) 2003 Texas Instruments, Incorporated. *
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* All Rights Reserved. *
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* ========================================================================= *
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.global _DSP_bitrev_cplx
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* ========================================================================= *
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* End of file: dsp_bitrev_cplx.h64 *
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* ------------------------------------------------------------------------- *
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* Copyright (c) 2003 Texas Instruments, Incorporated. *
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* All Rights Reserved. *
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* ========================================================================= *
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