Subversion Repositories pltbutils

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

-- pltbutils_time_measure

-- Measures high-time, low-time and period of a signal, usually a

-- clock.

-- Setting G_VERBOSITY to at least 20 reports measures times. 

-- Set G_RPT_LABEL to a prefix used in reports, typically the name

-- of the signal being measured. 

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

library ieee;

use ieee.std_logic_1164.all;

entity pltbutils_time_measure is

  generic (

    G_VERBOSITY     : integer := 0;

    G_RPT_LABEL     : string  := "pltbutils_time_measure"

  );

  port (

    t_hi_o          : out time;             -- High time

    t_lo_o          : out time;             -- Low time

    t_per_o         : out time;             -- Period time

    s_i             : in  std_logic         -- Signal to measure

  );

end entity pltbutils_time_measure;

architecture bhv of pltbutils_time_measure is

  signal   t_hi         : time := 0 ns;

  signal   t_lo         : time := 0 ns;

  signal   t_per        : time := 0 ns;

begin

  measure_p : process (s_i)

    variable last_rising_edge  : time := -1 ns;

    variable last_falling_edge : time := -1 ns;

  begin

    if rising_edge(s_i) then

      if last_falling_edge >= 0 ns then

        t_lo <= now - last_falling_edge;

      end if;

      if last_rising_edge >= 0 ns then

        t_per <= now - last_rising_edge;

      end if;

      last_rising_edge := now;

    end if;

    if falling_edge(s_i) then

      if last_rising_edge >= 0 ns then

        t_hi <= now - last_rising_edge;

      end if;

      last_falling_edge := now;

    end if;

  end process measure_p;

  assert not (G_VERBOSITY >  20 and t_lo'event)

    report G_RPT_LABEL & ": t_lo=" & time'image(t_lo)

    severity note;

  assert not (G_VERBOSITY >  20 and t_hi'event)

    report G_RPT_LABEL & ": t_hi=" & time'image(t_hi)

    severity note;

  assert not (G_VERBOSITY >  20 and t_per'event)

    report G_RPT_LABEL & ": t_hi=" & time'image(t_per)

    severity note;

  t_hi_o        <= t_hi;

  t_lo_o        <= t_lo;

  t_per_o       <= t_per;

end architecture bhv;

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

-- pltbutils_diff_check

-- Checks that the negative half of a diff pair is the

-- always the complement of the positive half.

-- Setting G_VERBOSITY to at least 100 reports number of diff errors.

-- Set G_RPT_LABEL to a prefix used in reports, typically the name

-- of the signal being measured. 

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

library ieee;

use ieee.std_logic_1164.all;

entity pltbutils_diff_check is

  generic (

    G_VERBOSITY     : integer := 0;

    G_RPT_LABEL     : string  := "pltbutils_diff_check"

  );

  port (

    diff_error_o    : out std_logic;        -- High when diff error detected

    diff_errors_o   : out integer;          -- Number of diff errors detected

    s_i             : in  std_logic;        -- Pos half of diff pair to check

    s_n_i           : in  std_logic := '0'; -- Neg half of diff pair to check

    rst_errors_i    : in  std_logic := '0'  -- High resets diff error counter

  );

end entity pltbutils_diff_check;

architecture bhv of pltbutils_diff_check is

  constant C_INTEGER_MAX : integer := (2**30) + ((2**30)-1); -- Equals (2**31)-1 without overflowing;

  signal   diff_error   : std_logic := '0';

  signal   diff_errors  : integer := 0;

begin

  diff_check_p : process (s_i, s_n_i, rst_errors_i)

  -- TODO: allow a small (configurable) timing tolerance between edges of s_i and s_n_i

  begin

    if s_i /= not s_n_i then

      diff_error  <= '1';

      if diff_errors < C_INTEGER_MAX then

        diff_errors <= diff_errors + 1;

      end if;

    else

      diff_error  <= '0';

    end if;

    if rst_errors_i = '1' then

      diff_errors <= 0;

    end if;

  end process diff_check_p;

  assert not (G_VERBOSITY > 100 and diff_errors'event)

    report G_RPT_LABEL & ": diff_errors=" & integer'image(diff_errors)

    severity note;

  diff_error_o  <= diff_error;

  diff_errors_o <= diff_errors;

end architecture bhv;