Revision 1528
Added by markw about 1 hour ago
| atari_chips/pokeyv2/mixer.vhdl | ||
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variable dc_cur : dc_acc_t;
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variable err : dc_acc_t;
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variable adj : dc_acc_t;
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variable dc_new_v : dc_acc_t;
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variable y_new : dc_acc_t;
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begin
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state_next <= state_reg;
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out_ch_next <= out_ch_reg;
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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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-- Cheap DC blocker:
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-- y = x - dc_old
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-- dc = dc_old + (y / 2**DC_K)
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--
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-- The previous version output x - dc_new, which costs an
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-- extra subtractor and differs only by y/2**DC_K.
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err := x_ext - dc_cur;
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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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adj := shift_right(err, DC_K);
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dc_next(ch_idx) <= dc_cur + adj;
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end if;
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dc_corrected_next <= resize(y_new, 20);
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dc_corrected_next <= resize(err, 20);
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clearAcc := '1';
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state_next <= state_clear;
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Simplify DC blocker to save some LEs