gfmul.tdf

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-------------------------------------------------------------------------
-------------------------------------------------------------------------
--
-- Revision Control Information
--
-- $Workfile:   GFMUL.TDF  $
-- $Archive:   P:/RS_eras/units/Common_units/ahdl/GFMUL.TDv  $
--
-- $Revision:   1.1  $
-- $Date:   14 Jul 1999 10:33:54  $
-- $Author			:  Alejandro Diaz-Manero
--
-- Project      :  RS_eras
--
-- Description	: 
--
-- Copyright 1999 (c) Altera Corporation
-- All rights reserved
--
-------------------------------------------------------------------------
-------------------------------------------------------------------------  

PARAMETERS
(
m = 8,       -- GF(2^m), minimum m = 3
irrpol = 391 -- irreducible polynomial
);

subdesign gfmul

(
a[m..1], b[m..1] : INPUT;
c[m..1] : OUTPUT;
)

VARIABLE

expand[m..2][(2*m-1)..1] : node;
total[m..1][(2*m-1)..1] : node;
irp[(m+1)..1] : node;
reduce[(m-1)..1][(2*m-1)..1] : node;
extra[(m-1)..1][(m+1)..1] : node;
left[(m-1)..1] : node;

BEGIN

irp[] = irrpol;

left[] = 0;

total[1][(2*m-1)..1] = (left[], (a[] & b[1]));

FOR k IN 2 TO m GENERATE

  IF (k<m) GENERATE
    FOR j IN (k+m) TO (2*m-1) GENERATE
      expand[k][j] = GND;
    END GENERATE;
  END GENERATE;

  FOR j IN 1 TO (k-1) GENERATE
    expand[k][j] = GND;
  END GENERATE;

  expand[k][(k+m-1)..k] = (a[] & b[k]);
  
  FOR j IN 1 TO (2*m-1) GENERATE
    total[k][j] = expand[k][j] $ total[k-1][j];
  END GENERATE;

END GENERATE;

FOR k IN 1 TO (m-1) GENERATE 

  IF (k == 1) GENERATE
    extra[k][] = irp[] & total[m][2*m-k];
  ELSE GENERATE
    extra[k][] = irp[] & reduce[k-1][2*m-k];
  END GENERATE;

  IF (k<(m-1) & k!=1) GENERATE
    FOR j IN 1 TO ((m-1)-k) GENERATE
      reduce[k][j] = reduce[k-1][j];
    END GENERATE;
  END GENERATE;

  IF (k == 1) GENERATE
    FOR j IN 1 TO (m-2) GENERATE
      reduce[1][j] = total[m][j];
    END GENERATE;
  END GENERATE;

  IF (k>1) GENERATE
    FOR j IN (m-k) TO (2*m-k) GENERATE
      reduce[k][j] = extra[k][j-(m-1)+k] $ reduce[k-1][j];
    END GENERATE;
  ELSE GENERATE
    FOR j IN (m-1) TO (2*m-1) GENERATE
       reduce[k][j] = total[m][j] $ extra[1][j-(m-2)];
    END GENERATE;
  END GENERATE;

-- make unused reduce nodes disappear by ANDing with 0
  IF (k>1) GENERATE
    reduce[k][2*m-k] = GND & reduce[k-1][2*m-1];
    FOR j IN (2*m-k+1) TO 2*m-1 GENERATE
      reduce[k][j] = GND & reduce[k][j-1];
    END GENERATE;
  END GENERATE;

END GENERATE;

c[m..2] = reduce[m-1][m..2];
c[1] = reduce[m-1][1] # reduce[m-1][2*m-1]; -- last term is disappeared reduce nodes

END;