66 lines
2.2 KiB
Plaintext
66 lines
2.2 KiB
Plaintext
// ---------------------------------------------------------------------------
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// This file is part of reSID, a MOS6581 SID emulator engine.
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// Copyright (C) 2010 Dag Lem <resid@nimrod.no>
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//
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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 2 of the License, or
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// (at your option) any later version.
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//
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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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//
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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, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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// ---------------------------------------------------------------------------
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#define RESID_EXTFILT_CC
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#include "extfilt.h"
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namespace reSID
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{
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// ----------------------------------------------------------------------------
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// Constructor.
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// ----------------------------------------------------------------------------
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ExternalFilter::ExternalFilter()
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{
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reset();
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enable_filter(true);
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// Low-pass: R = 10 kOhm, C = 1000 pF; w0l = 1/RC = 1/(1e4*1e-9) = 100 000
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// High-pass: R = 1 kOhm, C = 10 uF; w0h = 1/RC = 1/(1e3*1e-5) = 100
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// Assume a 1MHz clock.
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// Cutoff frequency accuracy (4 bits) is traded off for filter signal
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// accuracy (27 bits). This is crucial since w0lp and w0hp are so far apart.
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w0lp_1_s7 = int(100000*1.0e-6*(1 << 7) + 0.5);
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w0hp_1_s17 = int(100*1.0e-6*(1 << 17) + 0.5);
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}
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// ----------------------------------------------------------------------------
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// Enable filter.
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// ----------------------------------------------------------------------------
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void ExternalFilter::enable_filter(bool enable)
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{
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enabled = enable;
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}
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// ----------------------------------------------------------------------------
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// SID reset.
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// ----------------------------------------------------------------------------
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void ExternalFilter::reset()
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{
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// State of filter.
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Vlp = 0;
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Vhp = 0;
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}
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} // namespace reSID
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