crhelpers.vhdl

   1 library ieee;
   2 use ieee.std_logic_1164.all;
   3
   4 library work;
   5 use work.common.all;
   6
   7 package crhelpers is
   8     subtype crnum_t is integer range 0 to 7;
   9     subtype crmask_t is std_ulogic_vector(7 downto 0);
  10
  11     function fxm_to_num(fxm: crmask_t) return crnum_t;
  12     function num_to_fxm(num: crnum_t) return crmask_t;
  13 end package crhelpers;
  14
  15 package body crhelpers is
  16
  17     function fxm_to_num(fxm: crmask_t) return crnum_t is
  18     begin
  19         -- If multiple fields are set (undefined), match existing
  20         -- hardware by returning the first one.
  21         for i in 0 to 7 loop
  22             -- Big endian bit numbering
  23             if fxm(7-i) = '1' then
  24                 return i;
  25             end if;
  26         end loop;
  27
  28         -- If no fields are set (undefined), also match existing
  29         -- hardware by returning cr7.
  30         return 7;
  31     end;
  32
  33     function num_to_fxm(num: crnum_t) return crmask_t is
  34     begin
  35         case num is
  36             when 0 =>
  37                 return "10000000";
  38             when 1 =>
  39                 return "01000000";
  40             when 2 =>
  41                 return "00100000";
  42             when 3 =>
  43                 return "00010000";
  44             when 4 =>
  45                 return "00001000";
  46             when 5 =>
  47                 return "00000100";
  48             when 6 =>
  49                 return "00000010";
  50             when 7 =>
  51                 return "00000001";
  52             when others =>
  53                 return "00000000";
  54         end case;
  55     end;
  56
  57 end package body crhelpers;