fixed_pkg_c.vhdl

something i got you may find this useful

    constant right_index    : INTEGER;  -- size of fraction
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style;
    constant guard_bits     : NATURAL                   := fixed_guard_bits)
    return UNRESOLVED_sfixed;

  function to_sfixed (
    arg                     : REAL;     -- real
    size_res                : UNRESOLVED_sfixed;  -- for size only
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style;
    constant guard_bits     : NATURAL                   := fixed_guard_bits)
    return UNRESOLVED_sfixed;

  -- signed to sfixed
  function to_sfixed (
    arg                     : SIGNED;               -- signed
    constant left_index     : INTEGER;  -- size of integer portion
    constant right_index    : INTEGER                   := 0;  -- size of fraction
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style)
    return UNRESOLVED_sfixed;

  function to_sfixed (
    arg                     : SIGNED;  -- signed
    size_res                : UNRESOLVED_sfixed;  -- for size only
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style)
    return UNRESOLVED_sfixed;

  -- signed to sfixed (output assumed to be size of signed input)
  function to_sfixed (
    arg : SIGNED)            -- signed
    return UNRESOLVED_sfixed;

  -- Conversion from ufixed to sfixed
  function to_sfixed (
    arg : UNRESOLVED_ufixed)
    return UNRESOLVED_sfixed;

  -- signed fixed point to signed
  function to_signed (
    arg                     : UNRESOLVED_sfixed;  -- fixed point input
    constant size           : NATURAL;            -- length of output
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style)
    return SIGNED;

  -- signed fixed point to signed
  function to_signed (
    arg                     : UNRESOLVED_sfixed;  -- fixed point input
    size_res                : SIGNED;  -- used for length of output
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style)
    return SIGNED;

  -- signed fixed point to real
  function to_real (
    arg : UNRESOLVED_sfixed)            -- fixed point input
    return REAL;

  -- signed fixed point to integer
  function to_integer (
    arg                     : UNRESOLVED_sfixed;  -- fixed point input
    constant overflow_style : fixed_overflow_style_type := fixed_overflow_style;
    constant round_style    : fixed_round_style_type    := fixed_round_style)
    return INTEGER;

  -- Because of the fairly complicated sizing rules in the fixed point
  -- packages these functions are provided to compute the result ranges
  -- Example:
  -- signal uf1 : ufixed (3 downto -3);
  -- signal uf2 : ufixed (4 downto -2);
  -- signal uf1multuf2 : ufixed (ufixed_high (3, -3, '*', 4, -2) downto
  --                             ufixed_low (3, -3, '*', 4, -2));
  -- uf1multuf2 <= uf1 * uf2;
  -- Valid characters: '+', '-', '*', '/', 'r' or 'R' (rem), 'm' or 'M' (mod),
  --                   '1' (reciprocal), 'a' or 'A' (abs), 'n' or 'N' (unary -)
  function ufixed_high (left_index, right_index   : INTEGER;
                        operation                 : CHARACTER := 'X';
                        left_index2, right_index2 : INTEGER   := 0)
    return INTEGER;
  
  function ufixed_low (left_index, right_index   : INTEGER;
                       operation                 : CHARACTER := 'X';
                       left_index2, right_index2 : INTEGER   := 0)
    return INTEGER;
  
  function sfixed_high (left_index, right_index   : INTEGER;
                        operation                 : CHARACTER := 'X';
                        left_index2, right_index2 : INTEGER   := 0)
    return INTEGER;
  
  function sfixed_low (left_index, right_index   : INTEGER;
                       operation                 : CHARACTER := 'X';
                       left_index2, right_index2 : INTEGER   := 0)
    return INTEGER;

  -- Same as above, but using the "size_res" input only for their ranges:
  -- signal uf1multuf2 : ufixed (ufixed_high (uf1, '*', uf2) downto
  --                             ufixed_low (uf1, '*', uf2));
  -- uf1multuf2 <= uf1 * uf2;
  -- 
  function ufixed_high (size_res  : UNRESOLVED_ufixed;
                        operation : CHARACTER := 'X';
                        size_res2 : UNRESOLVED_ufixed)
    return INTEGER;
  
  function ufixed_low (size_res  : UNRESOLVED_ufixed;
                       operation : CHARACTER := 'X';
                       size_res2 : UNRESOLVED_ufixed)
    return INTEGER;
  
  function sfixed_high (size_res  : UNRESOLVED_sfixed;
                        operation : CHARACTER := 'X';
                        size_res2 : UNRESOLVED_sfixed)
    return INTEGER;
  
  function sfixed_low (size_res  : UNRESOLVED_sfixed;
                       operation : CHARACTER := 'X';
                       size_res2 : UNRESOLVED_sfixed)
    return INTEGER;

  -- purpose: returns a saturated number
  function saturate (
    constant left_index  : INTEGER;
    constant right_index : INTEGER)
    return UNRESOLVED_ufixed;

  -- purpose: returns a saturated number
  function saturate (
    constant left_index  : INTEGER;
    constant right_index : INTEGER)
    return UNRESOLVED_sfixed;

  function saturate (
    size_res : UNRESOLVED_ufixed)       -- only the size of this is used
    return UNRESOLVED_ufixed;

  function saturate (
    size_res : UNRESOLVED_sfixed)       -- only the size of this is used
    return UNRESOLVED_sfixed;

  --===========================================================================
  -- Translation Functions
  --===========================================================================

  -- maps meta-logical values
  function to_01 (
    s             : UNRESOLVED_ufixed;  -- fixed point input
    constant XMAP : STD_ULOGIC := '0')  -- Map x to
    return UNRESOLVED_ufixed;

  -- maps meta-logical values
  function to_01 (
    s             : UNRESOLVED_sfixed;  -- fixed point input
    constant XMAP : STD_ULOGIC := '0')  -- Map x to
    return UNRESOLVED_sfixed;

  function Is_X    (arg : UNRESOLVED_ufixed) return BOOLEAN;
  function Is_X    (arg : UNRESOLVED_sfixed) return BOOLEAN;
  function to_X01  (arg : UNRESOLVED_ufixed) return UNRESOLVED_ufixed;
  function to_X01  (arg : UNRESOLVED_sfixed) return UNRESOLVED_sfixed;
  function to_X01Z (arg : UNRESOLVED_ufixed) return UNRESOLVED_ufixed;
  function to_X01Z (arg : UNRESOLVED_sfixed) return UNRESOLVED_sfixed;
  function to_UX01 (arg : UNRESOLVED_ufixed) return UNRESOLVED_ufixed;
  function to_UX01 (arg : UNRESOLVED_sfixed) return UNRESOLVED_sfixed;

  -- straight vector conversion routines, needed for synthesis.
  -- These functions are here so that a std_logic_vector can be
  -- converted to and from sfixed and ufixed.  Note that you can
  -- not convert these vectors because of their negative index.
  
  function to_slv (
    arg : UNRESOLVED_ufixed)            -- fixed point vector
    return STD_LOGIC_VECTOR;
--  alias to_StdLogicVector is to_slv [UNRESOLVED_ufixed
--                                     return STD_LOGIC_VECTOR];
--  alias to_Std_Logic_Vector is to_slv [UNRESOLVED_ufixed
--                                       return STD_LOGIC_VECTOR];

  function to_slv (
    arg : UNRESOLVED_sfixed)            -- fixed point vector
    return STD_LOGIC_VECTOR;
--  alias to_StdLogicVector is to_slv [UNRESOLVED_sfixed
--                                     return STD_LOGIC_VECTOR];
--  alias to_Std_Logic_Vector is to_slv [UNRESOLVED_sfixed
--                                       return STD_LOGIC_VECTOR];

  function to_suv (
    arg : UNRESOLVED_ufixed)            -- fixed point vector
    return STD_ULOGIC_VECTOR;
--  alias to_StdULogicVector is to_suv [UNRESOLVED_ufixed
--                                      return STD_ULOGIC_VECTOR];
--  alias to_Std_ULogic_Vector is to_suv [UNRESOLVED_ufixed
--                                        return STD_ULOGIC_VECTOR];

  function to_suv (
    arg : UNRESOLVED_sfixed)            -- fixed point vector
    return STD_ULOGIC_VECTOR;
--  alias to_StdULogicVector is to_suv [UNRESOLVED_sfixed
--                                      return STD_ULOGIC_VECTOR];
--  alias to_Std_ULogic_Vector is to_suv [UNRESOLVED_sfixed
--                                        return STD_ULOGIC_VECTOR];

  function to_ufixed (
    arg                  : STD_ULOGIC_VECTOR;  -- shifted vector
    constant left_index  : INTEGER;
    constant right_index : INTEGER)
    return UNRESOLVED_ufixed;

  function to_ufixed (
    arg      : STD_ULOGIC_VECTOR;       -- shifted vector
    size_res : UNRESOLVED_ufixed)       -- for size only
    return UNRESOLVED_ufixed;

  function to_sfixed (
    arg                  : STD_ULOGIC_VECTOR;  -- shifted vector
    constant left_index  : INTEGER;
    constant right_index : INTEGER)
    return UNRESOLVED_sfixed;

  function to_sfixed (
    arg      : STD_ULOGIC_VECTOR;       -- shifted vector
    size_res : UNRESOLVED_sfixed)       -- for size only
    return UNRESOLVED_sfixed;

  -- As a concession to those who use a graphical DSP environment,
  -- these functions take parameters in those tools format and create
  -- fixed point numbers.  These functions are designed to convert from
  -- a std_logic_vector to the VHDL fixed point format using the conventions
  -- of these packages.  In a pure VHDL environment you should use the
  -- "to_ufixed" and "to_sfixed" routines.

  -- unsigned fixed point
  function to_UFix (
    arg      : STD_ULOGIC_VECTOR;
    width    : NATURAL;                 -- width of vector
    fraction : NATURAL)                 -- width of fraction
    return UNRESOLVED_ufixed;

  -- signed fixed point
  function to_SFix (
    arg      : STD_ULOGIC_VECTOR;
    width    : NATURAL;                 -- width of vector
    fraction : NATURAL)                 -- width of fraction
    return UNRESOLVED_sfixed;

  -- finding the bounds of a number.  These functions can be used like this:
  -- signal xxx : ufixed (7 downto -3);
  -- -- Which is the same as "ufixed (UFix_high (11,3) downto UFix_low(11,3))"
  -- signal yyy : ufixed (UFix_high (11, 3, "+", 11, 3)
  --               downto UFix_low(11, 3, "+", 11, 3));
  -- Where "11" is the width of xxx (xxx'length),
  -- and 3 is the lower bound (abs (xxx'low))
  -- In a pure VHDL environment use "ufixed_high" and "ufixed_low"
  
  function UFix_high (width, fraction   : NATURAL;
                      operation         : CHARACTER := 'X';
                      width2, fraction2 : NATURAL   := 0)
    return INTEGER;
  
  function UFix_low (width, fraction   : NATURAL;
                     operation         : CHARACTER := 'X';
                     width2, fraction2 : NATURAL   := 0)
    return INTEGER;

  -- Same as above but for signed fixed point.  Note that the width
  -- of a signed fixed point number ignores the sign bit, thus
  -- width = sxxx'length-1
  
  function SFix_high (width, fraction   : NATURAL;
                      operation         : CHARACTER := 'X';
                      width2, fraction2 : NATURAL   := 0)
    return INTEGER;
  
  function SFix_low (width, fraction   : NATURAL;
                     operation         : CHARACTER := 'X';
                     width2, fraction2 : NATURAL   := 0)
    return INTEGER;
-- rtl_synthesis off
-- pragma synthesis_off
  --===========================================================================