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Diffstat (limited to 'testsuite/gna/issue301/packages/pkg_trellis.vhd')
| -rw-r--r-- | testsuite/gna/issue301/packages/pkg_trellis.vhd | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/testsuite/gna/issue301/packages/pkg_trellis.vhd b/testsuite/gna/issue301/packages/pkg_trellis.vhd new file mode 100644 index 000000000..a797d3ac9 --- /dev/null +++ b/testsuite/gna/issue301/packages/pkg_trellis.vhd @@ -0,0 +1,185 @@ +--! +--! Copyright (C) 2011 - 2014 Creonic GmbH +--! +--! This file is part of the Creonic Viterbi Decoder, which is distributed +--! under the terms of the GNU General Public License version 2. +--! +--! @file +--! @brief Trellis parameter calculations (e.g., transitions, init values). +--! @author Markus Fehrenz +--! @date 2011/07/27 +--! +--! + +library ieee; +use ieee.std_logic_1164.all; +use ieee.numeric_std.all; + +library dec_viterbi; +use dec_viterbi.pkg_param.all; +use dec_viterbi.pkg_param_derived.all; +use dec_viterbi.pkg_types.all; + + +package pkg_trellis is + + type t_prev_base is array (1 downto 0) of std_logic_vector(BW_TRELLIS_STATES - 1 downto 0); + type t_previous_states is array (NUMBER_TRELLIS_STATES - 1 downto 0) of t_prev_base; + + type t_trans_base is array (1 downto 0) of std_logic_vector(NUMBER_PARITY_BITS - 1 downto 0); + type t_transitions is array (NUMBER_TRELLIS_STATES - 1 downto 0) of t_trans_base; + + type t_trans_base_signed is array (1 downto 0) of std_logic_vector(NUMBER_PARITY_BITS downto 0); + type t_transitions_signed is array (NUMBER_TRELLIS_STATES - 1 downto 0) of t_trans_base_signed; + + + -- + -- This function calculates the previous states of each state. + -- The values are used to connect the ACS units. + -- + function calc_previous_states return t_previous_states; + + + -- + -- This function calculates corresponding transitions to a trellis sate. + -- The values are used to connect branch units to ACS units. + -- + function calc_transitions return t_transitions; + + + -- + -- This function calculates the initialization values for trellis metrics. + -- The values are used as a constant and written to the ACS unit, every time a new block arrives. + -- + function calc_initialize return t_node_s; + + constant PREVIOUS_STATES : t_previous_states; + constant TRANSITIONS : t_transitions; + constant INITIALIZE_TRELLIS : t_node_s; + +end package pkg_trellis; + + +package body pkg_trellis is + + + function calc_previous_states return t_previous_states is + variable v_prev_states : t_previous_states := (others=>(others=>(others => '0'))); + variable v_state0, v_state1 : std_logic_vector(BW_TRELLIS_STATES - 1 downto 0); + begin + for i in NUMBER_TRELLIS_STATES - 1 downto 0 loop + v_state0 := std_logic_vector(to_unsigned(i,BW_TRELLIS_STATES)); + v_state1 := v_state0(BW_TRELLIS_STATES - 2 downto 0) & '0'; + v_prev_states(i)(0) := v_state1; + v_state1 := v_state0(BW_TRELLIS_STATES - 2 downto 0) & '1'; + v_prev_states(i)(1) := v_state1; + end loop; + return v_prev_states; + end function calc_previous_states; + + + function calc_transitions return t_transitions is + variable v_transitions : t_transitions_signed := (others => (others => (others => '0'))); + variable v_transitions_out : t_transitions := (others => (others => (others => '0'))); + variable v_one_transition : std_logic_vector(NUMBER_PARITY_BITS - 1 downto 0); + variable v_next_state : unsigned(ENCODER_MEMORY_DEPTH - 1 downto 0) := (others => '0'); + variable v_state, v_states : unsigned(ENCODER_MEMORY_DEPTH downto 0); + variable v_bit : std_logic := '0'; + begin + + -- + -- It is possible to reduce code size at this stage, if feedback is handled differently, + -- but the complexity will increase. + -- + + for i in NUMBER_TRELLIS_STATES - 1 downto 0 loop + + -- + -- for input : 0 + -- determine correct input with feedback + -- + v_next_state := to_unsigned(i,ENCODER_MEMORY_DEPTH) and to_unsigned(FEEDBACK_POLYNOMIAL, ENCODER_MEMORY_DEPTH); + for k in ENCODER_MEMORY_DEPTH - 1 downto 0 loop + v_bit := v_bit xor v_next_state(k); + end loop; + v_state(ENCODER_MEMORY_DEPTH) := v_bit; + v_state(ENCODER_MEMORY_DEPTH - 1 downto 0) := to_unsigned(i,ENCODER_MEMORY_DEPTH); + v_next_state := v_state(ENCODER_MEMORY_DEPTH downto 1); + v_bit := '0'; + + -- determine paritybits + for j in NUMBER_PARITY_BITS - 1 downto 0 loop + v_states := v_state and to_unsigned(PARITY_POLYNOMIALS(j), ENCODER_MEMORY_DEPTH + 1); + for k in ENCODER_MEMORY_DEPTH downto 0 loop + v_bit := v_bit xor v_states(k); + end loop; + v_one_transition(j) := v_bit; + v_bit := '0'; + end loop; + + -- decide where to save the parity result + if v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS) = '0' then + v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS) := '1'; + v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS - 1 downto 0) := v_one_transition; + else + v_transitions(to_integer(v_next_state))(0)(NUMBER_PARITY_BITS - 1 downto 0) := v_one_transition; + end if; + + -- + -- for input: 1 + -- determine correct input with feedback + -- + v_next_state := to_unsigned(i,ENCODER_MEMORY_DEPTH) and to_unsigned(FEEDBACK_POLYNOMIAL, ENCODER_MEMORY_DEPTH); + for k in ENCODER_MEMORY_DEPTH - 1 downto 0 loop + v_bit := v_bit xor v_next_state(k); + end loop; + v_state(ENCODER_MEMORY_DEPTH) := '1' xor v_bit; + v_state(ENCODER_MEMORY_DEPTH - 1 downto 0) := to_unsigned(i,ENCODER_MEMORY_DEPTH); + v_next_state := v_state(ENCODER_MEMORY_DEPTH downto 1); + v_bit := '0'; + + -- determine paritybits + for j in NUMBER_PARITY_BITS - 1 downto 0 loop + v_states := v_state and to_unsigned(PARITY_POLYNOMIALS(j), ENCODER_MEMORY_DEPTH + 1); + for k in ENCODER_MEMORY_DEPTH downto 0 loop + v_bit := v_bit xor v_states(k); + end loop; + v_one_transition(j) := v_bit; + v_bit := '0'; + end loop; + + -- decide where to save parity result + if v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS) = '0' then + v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS) := '1'; + v_transitions(to_integer(v_next_state))(1)(NUMBER_PARITY_BITS - 1 downto 0) := v_one_transition; + else + v_transitions(to_integer(v_next_state))(0)(NUMBER_PARITY_BITS - 1 downto 0) := v_one_transition; + end if; + end loop; + + -- truncate, the bit, used to decide where to save parity result + for i in NUMBER_TRELLIS_STATES - 1 downto 0 loop + v_transitions_out(i)(1) := v_transitions(i)(1)(NUMBER_PARITY_BITS - 1 downto 0); + v_transitions_out(i)(0) := v_transitions(i)(0)(NUMBER_PARITY_BITS - 1 downto 0); + end loop; + + return v_transitions_out; + end function calc_transitions; + + + function calc_initialize return t_node_s is + variable v_initialize : t_node_s; + begin + v_initialize(0) := to_signed(0, BW_MAX_PROBABILITY); + for i in NUMBER_TRELLIS_STATES - 1 downto 1 loop + v_initialize(i) := to_signed(- 2 ** (BW_MAX_PROBABILITY - 2), BW_MAX_PROBABILITY); + end loop; + return v_initialize; + end function calc_initialize; + + + constant PREVIOUS_STATES : t_previous_states := calc_previous_states; + constant TRANSITIONS : t_transitions := calc_transitions; + constant INITIALIZE_TRELLIS : t_node_s := calc_initialize; + +end package body pkg_trellis; |