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entactogen |
-- Copyright (c) 2010 Antonio de la Piedra
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-- This program is free software: you can redistribute it and/or modify
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-- it under the terms of the GNU General Public License as published by
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-- the Free Software Foundation, either version 3 of the License, or
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-- (at your option) any later version.
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-- This program is distributed in the hope that it will be useful,
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-- but WITHOUT ANY WARRANTY; without even the implied warranty of
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-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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-- GNU General Public License for more details.
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-- You should have received a copy of the GNU General Public License
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-- along with this program. If not, see <http://www.gnu.org/licenses/>.
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-- A VHDL model of the IEEE 802.15.4 physical layer.
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library IEEE;
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use IEEE.STD_LOGIC_1164.ALL;
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use IEEE.STD_LOGIC_UNSIGNED.ALL;
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use IEEE.numeric_std.ALL;
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entity sym_corr is
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generic (t_symbol: integer := 16);
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port( correlator_start :in std_logic;
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correlator_clk: in std_logic;
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correlator_rst: in std_logic;
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correlator_input_q: in std_logic;
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correlator_symbol: out std_logic_vector(3 downto 0));
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end sym_corr;
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architecture Behavioral of sym_corr is
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signal count_temp: integer range 0 to 17;
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signal chip_shr: std_logic_vector(15 downto 0);
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type sym_t is array (15 downto 0) of std_logic_vector(15 downto 0);
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type symbol_table is array (15 downto 0) of std_logic_vector(3 downto 0);
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type corr_value_t is array (15 downto 0) of integer;
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type max_fun_output is array (1 downto 0) of integer range 0 to 16;
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constant symbol_zero_q : std_logic_vector(15 downto 0) := "1101100111000010";
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constant symbol_table_q: symbol_table := ("1111",
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"1110",
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"1101",
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"1100",
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"1011",
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"1010",
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"1001",
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"1000",
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"0111",
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"0110",
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"0101",
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"0100",
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"0011",
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"0010",
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"0001",
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"0000");
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function bit_to_integer(input_value: std_logic) return integer is
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begin
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if (input_value = '0' ) then
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return 0;
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else
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return 1;
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end if;
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end function bit_to_integer;
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function max_vector(vector: corr_value_t ) return max_fun_output is
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variable temp: integer range 0 to 8;
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variable pos: integer range 0 to 16;
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begin
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temp := 0;
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for i in vector'range loop
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if vector(i) > temp then
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temp := vector(i);
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pos := i;
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end if;
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end loop;
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return max_fun_output'(temp, pos);
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end function max_vector;
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begin
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corr_shr: process(correlator_start, correlator_clk, correlator_rst)
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variable chip_reg: std_logic_vector(15 downto 0);
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begin
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if (correlator_rst = '1') then
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chip_reg := symbol_zero_q;
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elsif (rising_edge(correlator_clk) and correlator_start = '1') then
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chip_reg := std_logic_vector(unsigned(chip_reg) rol 1);
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end if;
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chip_shr <= chip_reg;
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end process;
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corr_counter: process(correlator_start, correlator_clk)
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variable count: integer range 0 to t_symbol + 1:= 0;
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begin
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if (rising_edge(correlator_clk) and correlator_start = '1') then
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count := count + 1;
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if (count = t_symbol + 1) then
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count := 1;
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end if;
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end if;
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count_temp <= count;
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end process;
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corr: process(correlator_start, correlator_clk, correlator_rst)
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variable reg: std_logic_vector(15 downto 0) := (others => '0');
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variable sym: sym_t;
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variable corr_value: corr_value_t;
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variable sym_pos: max_fun_output;
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begin
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if (correlator_rst = '1') then
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for i in 0 to 15 loop
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sym(i):= (others =>'0');
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corr_value(i) := 0;
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end loop;
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reg := (others => '0');
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elsif (rising_edge(correlator_clk) and correlator_start = '1') then
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reg := reg(14 downto 0) & correlator_input_q;
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sym(0):= sym(0)(14 downto 0) & chip_shr(0);
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sym(1):= sym(1)(14 downto 0) & chip_shr(2);
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sym(2):= sym(2)(14 downto 0) & chip_shr(4);
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sym(3):= sym(3)(14 downto 0) & chip_shr(6);
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sym(4):= sym(4)(14 downto 0) & chip_shr(8);
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sym(5):= sym(5)(14 downto 0) & chip_shr(10);
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sym(6):= sym(6)(14 downto 0) & chip_shr(12);
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sym(7):= sym(7)(14 downto 0) & chip_shr(14);
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sym(8):= sym(8)(14 downto 0) & not chip_shr(0);
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sym(9):= sym(9)(14 downto 0) & not chip_shr(2);
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sym(10):= sym(10)(14 downto 0) & not chip_shr(4);
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sym(11):= sym(11)(14 downto 0) & not chip_shr(6);
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sym(12):= sym(12)(14 downto 0) & not chip_shr(8);
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sym(13):= sym(13)(14 downto 0) & not chip_shr(10);
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sym(14):= sym(14)(14 downto 0) & not chip_shr(12);
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sym(15):= sym(15)(14 downto 0) & not chip_shr(14);
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-- We've got a new symbol !
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if (count_temp = t_symbol) then
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for i in 0 to 15 loop
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for j in 0 to 15 loop
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corr_value(i) := corr_value(i) + bit_to_integer(reg(j) and sym(i)(j));
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end loop;
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end loop;
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sym_pos := max_vector(corr_value);
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correlator_symbol <= symbol_table_q(sym_pos(0));
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for i in 0 to 15 loop
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corr_value(i) := 0;
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end loop;
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end if;
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end if;
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end process;
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end Behavioral;
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