arith_utils.vhd

来自「用VHDL实现的除法器,非常好使,仿真通过了」· VHDL 代码 · 共 57 行

-------------------------------------------------------------------------------
-- Description :
-- Package of utility functions used in code for arithmetic units.
-------------------------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;

-------------------------------------------------------------------------------

package arith_utils is
  
  function log2ceil (n : integer) return integer;

  function log2floor (n : integer) return integer;

end arith_utils;

-------------------------------------------------------------------------------

package body arith_utils is

  -- purpose: computes ceil(log2(n))
  function log2ceil (n : integer) return integer is
    variable m, p : integer;
  begin
    m := 0;
    p := 1;
    for i in 0 to n loop
      if p < n then
        m := m + 1;
        p := p * 2;
      end if;
    end loop;
    return m;
  end log2ceil;    

  -- purpose: computes floor(log2(n))
  function log2floor (n : integer) return integer is
    variable m, p : integer;
  begin
    m := -1;
    p := 1;
    for i in 0 to n loop
      if p <= n then
        m := m + 1;
        p := p * 2;
      end if;
    end loop;
    return m;
  end log2floor;    

end arith_utils;

-------------------------------------------------------------------------------