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[/] [kvcordic/] [trunk/] [sw/] [cordic.nac] - Blame information for rev 2

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1 2 kavi
//
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// Filename: cordic.nac
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// Purpose : N-address code (NAC) implementation for a fixed-point universal
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//           CORDIC supporting all directions (ROTATION, VECTORING) and
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//           operation modes (CIRCULAR, LINEAR, HYPERBOLIC).
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//           The arithmetic representation used is signed fixed-point
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//           (Q2.14S). The implementation is based partly on the following
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//           sources (as references):
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//           [1] The simple fixed-point CORDIC tools from:
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//           http://www.dcs.gla.ac.uk/~jhw/cordic/
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//           [2] Jorg Arndt, Matters Computational (free ebook):
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//           http://www.jjj.de/fxt/
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//           [3] Jean-Michel Muller, Elementary Functions: Algorithms and
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//           Implementation, Second Edition, Birkhauser, 2006.
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//           [4] Uwe Meyer-Baese, Digital Signal Processing with Field
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//           Programmable Gate Arrays, Third Edition, Springer, 2007.
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// Author  : Nikolaos Kavvadias (C) 2010
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// Date    : 01-Nov-2010
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// Revision: 0.3.0 (31/10/10)
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//           Initial version.
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//           0.3.1 (01/11/10)
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//           Some hand optimizations.
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//           0.3.2 (01/11/10)
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//           Interface changes, implementation of a unified CORDIC (can
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//           compute any function).
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//           0.3.3 (08/11/10)
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//           Replaced the three coefficient LUTs with a single one.
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//
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constant s16 0, 1, 2, 4, 14, 28, 15;
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globalvar s16 cordic_tab[42]={65535,8999,4184,2058,1025,512,256,128,64,32,16,8,4,2,16384,8192,4096,2048,1024,512,256,128,64,32,16,8,4,2,12867,7596,4013,2037,1022,511,255,127,63,31,15,7,3,1};
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procedure cordic (in s16 direction, in s16 mode, in s16 xin, in s16 yin, in s16 zin, out s16 xout, out s16 yout, out s16 zout)
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{
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  localvar s16 k, d;
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  localvar s16 x, y, z;
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  localvar s16 xbyk, ybyk, i, tabval;
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  localvar s16 t0, t1, t2, t3, t4, t5, t6, t7;
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  localvar s16 zero, one, ldirection, lmode, offset;
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S_1:
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  zero <= ldc 0;
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  one <= ldc 1;
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  x <= mov xin;
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  y <= mov yin;
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  z <= mov zin;
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  ldirection <= mov direction;
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  lmode <= mov mode;
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//  kstart = ((mode == HYPERBOLIC) ? 1 : 0);
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  k <= muxeq lmode, 2, one, zero;
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//  offset = ((mode == HYPERBOLIC) ? 0 : ((mode == LINEAR) ? 14 : 28));
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  t0 <= muxeq lmode, 1, 14, 28;
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  offset <= muxeq lmode, 2, 0, t0;
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  i <= ldc 4;
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  S_2 <= jmpun;
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//  for (k = kstart; k < CORDIC_NTAB; ++k) {
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S_2:
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  S_3, S_EXIT <= jmplt k, 14;
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//again:
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S_3:
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  // precompute invariants: y>>k, -(y>>k), x>>k, cordic_ctab[k]
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  t0 <= shr y, k;
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  t1 <= neg t0;
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//  xbyk = (x>>k);
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  xbyk <= shr x, k;
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//  ybyk = ((mode == HYPERBOLIC) ? -(y>>k) : ((mode == LINEAR) ? 0 : (y>>k)));
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  t5 <= muxeq lmode, 1, zero, t0;
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  ybyk <= muxeq lmode, 2, t1, t5;
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//  tabval = ((mode == HYPERBOLIC) ? cordic_htab[k] : ((mode == LINEAR) ? cordic_btab[k] : cordic_ctab[k]));
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  t2 <= add k, offset;
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  tabval <= load cordic_tab, t2;
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//  if (direction == ROTATION) {
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//    d = ((z>=0) ? 0 : 1);
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  t7 <= shr z, 15;
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  t1 <= muxeq t7, 0, zero, one;
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//  } else { // VECTORING
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//    d = ((y<0) ? 0 : 1);
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//  }
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  t2 <= shr y, 15;
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  t3 <= muxne t2, 0, zero, one;
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  d <= muxeq ldirection, 0, t1, t3;
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  S_4, S_5 <= jmpeq d, 0;
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S_4:
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//   x = x - ybyk;
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  x <= sub x, ybyk;
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//   y = y + xbyk;
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  y <= add y, xbyk;
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//   z = z - tabval;
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  z <= sub z, tabval;
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  S_6 <= jmpun;
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S_5:
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//  x = x + ybyk;
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  x <= add x, ybyk;
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//  y = y - xbyk;
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  y <= sub y, xbyk;
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//  z = z + tabval;
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  z <= add z, tabval;
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  S_6 <= jmpun;
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S_6:
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//  if ((k == i) && (mode == HYPERBOLIC)) {
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  t0 <= seteq k, i;
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  t1 <= seteq lmode, 2;
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  t2 <= and t0, t1;
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  S_7, S_8 <= jmpeq t2, 1;
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S_7:
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//    i = ((i << 1) + i) + 1;
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//    goto again;
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//  }
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  t3 <= shl i, 1;
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  t4 <= add t3, i;
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  i <= add t4, 1;
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  S_3 <= jmpun;
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S_8:
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  k <= add k, 1;
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  S_2 <= jmpun;
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S_EXIT:
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  xout <= mov x;
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  yout <= mov y;
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  zout <= mov z;
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}

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