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128 lines
9.6 KiB
128 lines
9.6 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: 1.14 Thu Jun 12 17:41:04 2003 (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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* *
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* TEXAS INSTRUMENTS, INC. *
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* *
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* NAME *
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* DSP_fir_gen: FIR Filter (general purpose) *
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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_fir_gen *
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* ( *
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* const short *restrict x, /* Input ('nr + nh - 1' samples) */ *
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* const short *restrict h, /* Filter coefficients (nh taps) */ *
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* short *restrict r, /* Output array ('nr' samples) */ *
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* int nh, /* Length of filter (nh >= 5) */ *
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* int nr /* Length of output (nr >= 1) */ *
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* ); *
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* *
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* C CODE *
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* *
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* This is the C equivalent of the assembly code. Note that the *
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* assembly code is hand optimized and restrictions may apply. *
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* *
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* void DSP_fir_gen *
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* ( *
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* const short *restrict x, /* Input ('nr + nh - 1' samples) */ *
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* const short *restrict h, /* Filter coefficients (nh taps) */ *
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* short *restrict r, /* Output array ('nr' samples) */ *
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* int nh, /* Length of filter (nh >= 5) */ *
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* int nr /* Length of output (nr >= 1) */ *
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* ) *
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* { *
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* int i, j, sum; *
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* *
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* for (j = 0; j < nr; j++) *
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* { *
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* sum = 0; *
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* for (i = 0; i < nh; i++) *
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* sum += x[i + j] * h[i]; *
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* *
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* r[j] = sum >> 15; *
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* } *
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* } *
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* *
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* DESCRIPTION *
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* Computes a real FIR filter (direct-form) using coefficients *
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* stored in vector h. The real data input is stored in vector x. *
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* The filter output result is stored in vector r. This FIR *
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* assumes the number of filter coefficients is greater than or *
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* equal to 5. It operates on 16-bit data with a 32-bit *
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* accumulate. This routine has no memory hits regardless of where *
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* x, h, and r arrays are located in memory. The filter is nr *
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* output samples and nh coefficients. The assembly routine *
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* performs 4 output samples at a time. *
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* *
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* TECHNIQUES *
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* 1. Load double word instruction is used to simultaneously load *
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* four values in a single clock cycle. *
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* *
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* 2. The inner loop is unrolled four times and will always *
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* compute a multiple of 4 of nh and nr. If nh % 4 != 0, the *
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* code will fill in 0s to make nh a multiple of 4. If nr % 4 *
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* != 0, the code will still perform a mutiple of 4 outputs. *
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* *
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* 3. Both the inner and outer loops are software pipelined. *
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* *
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* 4. This code yields best performance when ratio of outer *
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* loop to inner loop is less than or equal to 4. *
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* *
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* ASSUMPTIONS *
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* 1. Little Endian is assumed for LDNDW. *
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* 2. nh >= 5. *
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* 3. nr multiple of 4. *
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* 4. Output array r[] must be word-aligned *
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* *
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* MEMORY NOTE *
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* No memory bank hits under any conditions. *
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* Little Endian operation is assumed. *
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* *
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* CYCLES *
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* [11 + 4 * ceil(nh/4)] * nr/4 + 15 *
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* *
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* CODESIZE *
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* 544 bytes *
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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_fir_gen
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* ========================================================================= *
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* End of file: dsp_fir_gen.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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