87 lines
1.9 KiB
VHDL
87 lines
1.9 KiB
VHDL
library ieee;
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use ieee.std_logic_1164.all;
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entity parser is
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port (
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clk : in std_logic;
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reset : in std_logic;
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is_record : in std_logic;
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is_data : out std_logic;
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char : in character;
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num1, num2 : out natural range 0 to 99;
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letter : out character
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);
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end entity;
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architecture behaviour of parser is
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type state_t is (S_NUM1, S_NUM2, S_LETTER, S_COLON, S_END_SPACE, S_DATA);
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signal state : state_t := S_NUM1;
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subtype digit is natural range 0 to 9;
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type multiples_lookup_t is array(digit) of natural range 0 to 90;
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constant TEN_MULTIPLES : multiples_lookup_t := (0, 10, 20, 30, 40, 50, 60, 70, 80, 90);
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-- most significant digit of number
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signal prev_digit : digit := 0;
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signal current_digit : digit;
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signal complete_num : natural range 0 to 99;
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function char_to_digit(input : in character) return digit is
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begin
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if not (input < '0') and input <= '9' then
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return character'pos(input) - character'pos('0');
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else
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return 0;
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end if;
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end function;
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begin
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current_digit <= char_to_digit(char);
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complete_num <= TEN_MULTIPLES(prev_digit) + current_digit;
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process(clk)
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begin
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if rising_edge(clk) then
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if reset then
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prev_digit <= 0;
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state <= S_NUM1;
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else
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prev_digit <= 0;
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case state is
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when S_NUM1 =>
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if is_record then
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if char = '-' then
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state <= S_NUM2;
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else
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num1 <= complete_num;
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prev_digit <= current_digit;
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end if;
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end if;
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when S_NUM2 =>
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if char = ' ' then
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state <= S_LETTER;
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else
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num2 <= complete_num;
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prev_digit <= current_digit;
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end if;
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when S_LETTER =>
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letter <= char;
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state <= S_COLON;
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when S_COLON =>
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state <= S_END_SPACE;
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when S_END_SPACE =>
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state <= S_DATA;
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when S_DATA =>
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if not is_record then
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state <= S_NUM1;
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end if;
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end case;
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end if;
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end if;
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end process;
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is_data <= '1' when state = S_DATA else '0';
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end architecture;
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