hw/qcounter.vhd

   1 library ieee;
   2 use ieee.std_logic_1164.all;
   3 use ieee.std_logic_arith.all;
   4 use ieee.std_logic_unsigned.all;
   5 use ieee.numeric_std.all;
   6 use work.lx_rocon_pkg.all;
   7
   8 -- Quadcounter (for IRC)
   9
  10 entity qcounter is
  11   port
  12         (
  13                 -- Inputs
  14     clk_i                : in std_logic;
  15     reset_i              : in std_logic;
  16     a0_i, b0_i           : in std_logic;
  17                 index0_i             : in std_logic;
  18                 -- State
  19                 reset_index_event_i  : in std_logic;
  20                 reset_index_event2_i : in std_logic;
  21                 reset_ab_error_i     : in std_logic;
  22                 -- Outputs
  23     qcount_o             : out std_logic_vector (7 downto 0);
  24                 qcount_index_o       : out std_logic_vector (7 downto 0);
  25                 index_event_o        : out std_logic;
  26                 index_event2_o       : out std_logic;
  27     a_rise_o, a_fall_o   : out std_logic;
  28                 b_rise_o, b_fall_o   : out std_logic;
  29                 ab_event_o           : out std_logic;
  30     ab_error_o           : out std_logic
  31   );
  32 end qcounter;
  33
  34 architecture behavioral of qcounter is
  35
  36         signal last_reset_s       : std_logic;
  37   signal a_s, b_s           : std_logic;
  38         signal a_prev_s, b_prev_s : std_logic;
  39         signal ab_error_s         : std_logic;
  40         signal ab_error_int_s     : std_logic;
  41         signal index_event_s      : std_logic;
  42         signal index_event_int_s  : std_logic;
  43         signal index_event2_s     : std_logic;
  44         signal index_event2_int_s : std_logic;
  45         signal index_s            : std_logic;
  46   signal count_prev_s       : std_logic_vector (5 downto 0);
  47   signal count_s            : std_logic_vector (5 downto 0);
  48         signal count_index_prev_s : std_logic_vector (7 downto 0);
  49   signal count_index_s      : std_logic_vector (7 downto 0);
  50
  51 begin
  52 dff_a: dff2
  53         port map
  54         (
  55                 clk_i   => clk_i,
  56                 reset_i => '0',
  57                 d_i     => a0_i,
  58                 q_o     => a_s
  59         );
  60
  61  dff_b: dff2
  62         port map
  63         (
  64                 clk_i   => clk_i,
  65                 reset_i => '0',
  66                 d_i     => b0_i,
  67                 q_o     => b_s
  68         );
  69
  70 dff_index: dff2
  71         port map
  72         (
  73                 clk_i   => clk_i,
  74                 reset_i => '0',
  75                 d_i     => index0_i,
  76                 q_o     => index_s
  77         );
  78
  79         qcount_o(0)           <= a_s xor b_s;
  80         qcount_o(1)           <= b_s;
  81         qcount_o(7 downto 2)  <= count_s;
  82         --
  83         qcount_index_o        <= count_index_s;
  84         --
  85         ab_error_o            <= ab_error_int_s;
  86         index_event_o         <= index_event_int_s;
  87         index_event2_o        <= index_event2_int_s;
  88
  89 comb_event:
  90         process (reset_i, last_reset_s, a_prev_s, b_prev_s, a_s, b_s)
  91         begin
  92     a_rise_o   <= '0';
  93     a_fall_o   <= '0';
  94     b_rise_o   <= '0';
  95     b_fall_o   <= '0';
  96     ab_event_o <= '0';
  97     ab_error_s <= '0';
  98
  99                 if reset_i = '0' and last_reset_s = '0' then
 100                         if ((a_s xor a_prev_s) and (b_s xor b_prev_s)) = '1' then
 101                                 -- forbidden double transition
 102                                 ab_error_s <= '1';
 103                                 ab_event_o <= '0';
 104                         else
 105                                 a_rise_o   <= (a_s xor a_prev_s) and a_s;
 106                                 a_fall_o   <= (a_s xor a_prev_s) and (not a_s);
 107                                 b_rise_o   <= (b_s xor b_prev_s) and b_s;
 108                                 b_fall_o   <= (b_s xor b_prev_s) and (not b_s);
 109                                 ab_event_o <= (a_s xor a_prev_s) or (b_s xor b_prev_s);
 110                         end if;
 111                 end if;
 112   end process;
 113
 114 comb_count:
 115         process (reset_i, last_reset_s, a_prev_s, b_prev_s, a_s, b_s,
 116                                                 index_s, count_prev_s, count_index_prev_s)
 117         begin
 118
 119                 index_event_s <= '0';
 120
 121                 if reset_i = '1' or last_reset_s = '1' then
 122                         count_s                      <= count_prev_s;
 123                         count_index_s                <= count_index_prev_s;
 124                 elsif (a_prev_s = '0') and (b_prev_s = '1') and (a_s = '0') and
 125                                                 (b_s = '0') then
 126       count_s                      <= count_prev_s + 1;
 127                         if index_s = '1' then
 128                                 count_index_s(0)           <= a_s xor b_s;
 129                                 count_index_s(1)           <= b_s;
 130                                 count_index_s(7 downto 2)  <= count_prev_s + 1;
 131                         else
 132                                 count_index_s              <= count_index_prev_s;
 133                         end if;
 134     elsif (a_prev_s = '0') and (b_prev_s = '0') and (a_s = '0') and
 135                                                 (b_s = '1') then
 136       count_s                      <= count_prev_s - 1;
 137
 138                         if index_s = '1' then
 139                                 count_index_s(0)           <= a_s xor b_s;
 140                                 count_index_s(1)           <= b_s;
 141                                 count_index_s(7 downto 2)  <= count_prev_s - 1;
 142                                 index_event_s              <= '1';
 143                         else
 144                                 count_index_s              <= count_index_prev_s;
 145                         end if;
 146     else
 147       count_s                      <= count_prev_s;
 148                         if index_s = '1' then
 149                                 count_index_s(0)           <= a_s xor b_s;
 150                                 count_index_s(1)           <= b_s;
 151                                 count_index_s(7 downto 2)  <= count_prev_s;
 152                                 index_event_s              <= '1';
 153                         else
 154                                 count_index_s              <= count_index_prev_s;
 155                         end if;
 156     end if;
 157
 158   end process;
 159
 160 seq:
 161         process
 162         begin
 163                 -- Reset for qcounter is synchronous and lasts at least one more cycle
 164                 -- to prevent hazardous states after releasing it
 165                 wait until clk_i'event and clk_i = '1';
 166
 167                 if reset_i = '1' then
 168                         count_prev_s        <= (others => '0');
 169                         count_index_prev_s  <= (others => '0');
 170                         index_event_int_s   <= '0';
 171                         index_event2_int_s  <= '0';
 172                         ab_error_int_s      <= '0';
 173                 else
 174                         count_prev_s        <= count_s;
 175                         count_index_prev_s  <= count_index_s;
 176                         --
 177                         if reset_index_event_i = '1' then
 178                                 index_event_int_s <= '0';
 179                         else
 180                                 index_event_int_s <= index_event_int_s or index_event_s;
 181                         end if;
 182                         --
 183                         if reset_index_event2_i = '1' then
 184                                 index_event2_int_s <= '0';
 185                         else
 186                                 index_event2_int_s <= index_event2_int_s or index_event_s;
 187                         end if;
 188                         --
 189                         if reset_ab_error_i = '1' then
 190                                 ab_error_int_s    <= '0';
 191                         else
 192                                 ab_error_int_s    <= ab_error_int_s or ab_error_s;
 193                         end if;
 194                 end if;
 195                 a_prev_s              <= a_s;
 196                 b_prev_s              <= b_s;
 197                 last_reset_s          <= reset_i;
 198   end process;
 199
 200 end behavioral;