伪随机数产生器 ----------------------------------------------------------------------------- -- -- The following information has been generated by Exemplar Logic and -- may be freely distributed and modified. -- -- Design name : pseudorandom -- -- Purpose : This design is a pseudorandom number generator. This design -- will generate an 8-bit random number using the polynomial p(x) = x + 1. -- This system has a seed generator and will generate 2**8 - 1 unique -- vectors in pseudorandom order. These vectors are stored in a ram which -- samples the random number every 32 clock cycles. This variance of a -- priority encoded seed plus a fixed sampling frequency provides a truely -- random number. -- -- This design used VHDL-1993 methods for coding VHDL. -- ----------------------------------------------------------------------------

Library IEEE ; use IEEE.std_logic_1164.all ; use IEEE.std_logic_arith.all ;

entity divide_by_n is generic (data_width : natural := 8 ); port ( data_in : in UNSIGNED(data_width - 1 downto 0) ; load : in std_logic ; clk : in std_logic ; reset : in std_logic ; divide : out std_logic ); end divide_by_n ; architecture rtl of divide_by_n is signal count_reg : UNSIGNED(data_width - 1 downto 0) ; constant max_count : UNSIGNED(data_width - 1 downto 0) := (others => '1') ; begin cont_it : process(clk,reset) begin if (reset = '1') then count_reg <= (others => '0') ; elsif (clk = '1' and clk'event) then if (load = '1') then count_reg <= data_in ; else count_reg <= count_reg + "01" ; end if ; end if; end process ; divide <= '1' when count_reg = max_count else '0' ; end RTL ;

Library IEEE ; use IEEE.std_logic_1164.all ; use IEEE.std_logic_arith.all ;

entity dlatrg is generic (data_width : natural := 16 ); port ( data_in : in UNSIGNED(data_width - 1 downto 0) ; clk : in std_logic ; reset : in std_logic ; data_out : out UNSIGNED(data_width - 1 downto 0) ); end dlatrg ;

architecture rtl of dlatrg is begin latch_it : process(data_in,clk,reset) begin if (reset = '1') then data_out <= (others => '0') ; elsif (clk = '1') then data_out <= data_in ; end if; end process ; end RTL ;

Library IEEE ; use IEEE.std_logic_1164.all ; use IEEE.std_logic_arith.all ;

entity lfsr is generic (data_width : natural := 8 ); port ( clk : in std_logic ; reset : in std_logic ; data_out : out UNSIGNED(data_width - 1 downto 0) ); end lfsr ;

architecture rtl of lfsr is signal feedback : std_logic ; signal lfsr_reg : UNSIGNED(data_width - 1 downto 0) ; begin feedback <= lfsr_reg(7) xor lfsr _reg(0) ; latch_it : process(clk,reset) begin if (reset = '1') then lfsr_reg <= (others => '0') ; elsif (clk = '1' and clk'event) then lfsr_reg <= lfsr_reg(lfsr_reg'high - 1 downto 0) & feedback ; end if; end process ; data_out <= lfsr_reg ; end RTL ;

Library IEEE ; use IEEE.std_logic_1164.all ; use IEEE.std_logic_arith.all ;

entity priority_encoder is generic (data_width : natural := 25 ; address_width : natural := 5 ) ; port ( data : in UNSIGNED(data_width - 1 downto 0) ; address : out UNSIGNED(address_width - 1 downto 0) ; none : out STD_LOGIC ); end priority_encoder ;

architecture rtl of priority_encoder is attribute SYNTHESIS_RETURN : STRING ;

FUNCTION to_stdlogic (arg1:BOOLEAN) RETURN STD_LOGIC IS BEGIN IF(arg1) THEN RETURN('1') ; ELSE RETURN('0') ; END IF ; END ;

function to_UNSIGNED(ARG: INTEGER; SIZE: INTEGER) return UNSIGNED is variable result: UNSIGNED(SIZE-1 downto 0); variable temp: integer; attribute SYNTHESIS_RETURN of result:variable is "FEED_THROUGH" ; begin temp := ARG; for i in 0 to SIZE-1 loop if (temp mod 2) = 1 then result(i) := '1'; else result(i) := '0'; end if; if temp > 0 then temp := temp / 2; else temp := (temp - 1) / 2; end if; end loop; return result; end;

constant zero : UNSIGNED(data_width downto 1) := (others => '0') ;