--!
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--!
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--! Copyright (C) 2011 - 2012 Creonic GmbH
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--! Copyright (C) 2011 - 2014 Creonic GmbH
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--!
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--!
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--! This file is part of the Creonic Viterbi Decoder, which is distributed
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--! This file is part of the Creonic Viterbi Decoder, which is distributed
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--! under the terms of the GNU General Public License version 2.
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--! under the terms of the GNU General Public License version 2.
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--!
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--!
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--! @file
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--! @file
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--! @brief Derived parameters
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--! @brief Derived parameters
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--! @author Markus Fehrenz
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--! @author Markus Fehrenz
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--! @date 2011/07/04
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--! @date 2011/07/04
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--!
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--!
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--! @details This constants are derived from constants defined in pkg_param.
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--! @details This constants are derived from constants defined in pkg_param.
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--! In order to prevent errors, there is no user choice for these parameters.
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--! In order to prevent errors, there is no user choice for these parameters.
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--!
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--!
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library ieee;
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_1164.all;
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use ieee.numeric_std.all;
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use ieee.numeric_std.all;
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library dec_viterbi;
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library dec_viterbi;
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use dec_viterbi.pkg_param.all;
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use dec_viterbi.pkg_param.all;
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use dec_viterbi.pkg_helper.all;
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use dec_viterbi.pkg_helper.all;
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package pkg_param_derived is
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package pkg_param_derived is
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-- Calculation of constraint length.
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-- Calculation of constraint length.
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function calc_constraint_length return natural;
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function calc_constraint_length return natural;
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-- Memory depth of the encoder shift register.
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-- Memory depth of the encoder shift register.
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constant ENCODER_MEMORY_DEPTH : natural;
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constant ENCODER_MEMORY_DEPTH : natural;
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-- Number of trellis states corresponds to the nubmer of ACS units.
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-- Number of trellis states corresponds to the nubmer of ACS units.
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constant NUMBER_TRELLIS_STATES : natural;
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constant NUMBER_TRELLIS_STATES : natural;
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-- Number of branch units for a single polynomial set
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-- Number of branch units for a single polynomial set
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constant NUMBER_BRANCH_UNITS : natural;
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constant NUMBER_BRANCH_UNITS : natural;
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-- Bitwidth constants are needed for type conversions
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-- Bitwidth constants are needed for type conversions
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constant BW_TRELLIS_STATES : natural;
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constant BW_TRELLIS_STATES : natural;
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constant BW_MAX_WINDOW_LENGTH : natural;
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constant BW_MAX_WINDOW_LENGTH : natural;
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constant BW_BRANCH_RESULT : natural;
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constant BW_BRANCH_RESULT : natural;
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constant BW_MAX_PROBABILITY : natural;
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constant BW_MAX_PROBABILITY : natural;
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end package pkg_param_derived;
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end package pkg_param_derived;
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package body pkg_param_derived is
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package body pkg_param_derived is
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function calc_constraint_length return natural is
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function calc_constraint_length return natural is
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variable v_maximum : natural := 0;
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variable v_maximum : natural := 0;
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begin
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begin
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-- Find the position of the leftmost bit in the polynomials.
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-- Find the position of the leftmost bit in the polynomials.
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for i in NUMBER_PARITY_BITS - 1 downto 0 loop
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for i in NUMBER_PARITY_BITS - 1 downto 0 loop
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v_maximum := max(v_maximum, no_bits_natural(PARITY_POLYNOMIALS(i)));
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v_maximum := max(v_maximum, no_bits_natural(PARITY_POLYNOMIALS(i)));
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end loop;
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end loop;
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v_maximum := max(v_maximum, no_bits_natural(FEEDBACK_POLYNOMIAL));
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v_maximum := max(v_maximum, no_bits_natural(FEEDBACK_POLYNOMIAL));
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return v_maximum;
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return v_maximum;
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end function calc_constraint_length;
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end function calc_constraint_length;
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constant ENCODER_MEMORY_DEPTH : natural := calc_constraint_length - 1;
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constant ENCODER_MEMORY_DEPTH : natural := calc_constraint_length - 1;
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constant NUMBER_TRELLIS_STATES : natural := 2 ** ENCODER_MEMORY_DEPTH;
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constant NUMBER_TRELLIS_STATES : natural := 2 ** ENCODER_MEMORY_DEPTH;
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constant NUMBER_BRANCH_UNITS : natural := 2 ** NUMBER_PARITY_BITS;
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constant NUMBER_BRANCH_UNITS : natural := 2 ** NUMBER_PARITY_BITS;
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constant BW_TRELLIS_STATES : natural := no_bits_natural(NUMBER_TRELLIS_STATES - 1);
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constant BW_TRELLIS_STATES : natural := no_bits_natural(NUMBER_TRELLIS_STATES - 1);
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constant BW_MAX_WINDOW_LENGTH : natural := no_bits_natural(MAX_WINDOW_LENGTH - 1);
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constant BW_MAX_WINDOW_LENGTH : natural := no_bits_natural(MAX_WINDOW_LENGTH - 1);
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constant BW_BRANCH_RESULT : natural := no_bits_natural((2 ** (BW_LLR_INPUT - 1)) * NUMBER_PARITY_BITS) + 1;
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constant BW_BRANCH_RESULT : natural := no_bits_natural((2 ** (BW_LLR_INPUT - 1)) * NUMBER_PARITY_BITS) + 1;
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constant BW_MAX_PROBABILITY : natural := no_bits_natural(((2 ** (BW_LLR_INPUT - 1)) * NUMBER_PARITY_BITS) * 4 * ENCODER_MEMORY_DEPTH);
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constant BW_MAX_PROBABILITY : natural := no_bits_natural(((2 ** (BW_LLR_INPUT - 1)) * NUMBER_PARITY_BITS) * 4 * ENCODER_MEMORY_DEPTH);
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end package body pkg_param_derived;
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end package body pkg_param_derived;
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