Revision 1524
Added by markw about 14 hours ago
| atari_chips/pokeyv2/mixer.vhdl | ||
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process(state_reg,RIGHT_REG,out_ch_reg,acc_reg,volume,dc_reg,dc_corrected_reg,
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POST_DIVIDE,SATURATED,include_in_output)
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POST_DIVIDE,SATURATED,include_in_output,enable_cycle)
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variable postdivide : std_logic_vector(1 downto 0);
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variable presaturate : signed(19 downto 0);
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variable addAcc : std_logic;
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| ... | ... | |
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ch_idx := to_integer(unsigned(out_ch_reg));
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x_ext := resize(presaturate, DC_ACC_WIDTH);
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dc_cur := dc_reg(ch_idx);
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err := x_ext - dc_cur;
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adj := shift_right(err, DC_K);
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-- shift_right on signed rounds toward -inf, so any err in
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-- (0, 2^DC_K) truncates adj to 0 and dc_reg gets stuck.
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-- Concretely: with x_ext=0 and dc_cur in [-1023,0], err is
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-- in [0,1023], adj=0, dc_new_v=dc_cur (frozen), and the
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-- output y_new = -dc_cur sits at a non-zero plateau forever.
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-- Force a unit step in err's direction whenever the natural
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-- decay would round to zero. This guarantees monotonic
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-- convergence of dc_reg toward x_ext for any input.
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if err > 0 and adj = 0 then
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adj := to_signed(1, DC_ACC_WIDTH);
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elsif err < 0 and adj = 0 then
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adj := to_signed(-1, DC_ACC_WIDTH);
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if ENABLE_CYCLE = '1' then
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err := x_ext - dc_cur;
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adj := shift_right(err, DC_K);
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dc_new_v := dc_cur + adj;
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dc_next(ch_idx) <= dc_new_v;
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y_new := x_ext - dc_new_v;
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else
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y_new := x_ext - dc_cur;
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end if;
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dc_new_v := dc_cur + adj;
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y_new := x_ext - dc_new_v;
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dc_next(ch_idx) <= dc_new_v;
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dc_corrected_next <= resize(y_new, 20);
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clearAcc := '1';
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state_next <= state_clear;
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Fix the lost bass