//  ---------------------------------------------------------------------------
//  This file is part of reSID, a MOS6581 SID emulator engine.
//  Copyright (C) 2004  Dag Lem <resid@nimrod.no>
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//  ---------------------------------------------------------------------------

#define __WAVE_CC__
#include "resid-fp/wave.h"

// ----------------------------------------------------------------------------
// Constructor.
// ----------------------------------------------------------------------------
WaveformGeneratorFP::WaveformGeneratorFP() {
	sync_source = this;

	set_chip_model(MOS6581FP);

	reset();
}

// ----------------------------------------------------------------------------
// Set sync source.
// ----------------------------------------------------------------------------
void WaveformGeneratorFP::set_sync_source(WaveformGeneratorFP *source) {
	sync_source = source;
	source->sync_dest = this;
}

// ----------------------------------------------------------------------------
// Set chip model.
// ----------------------------------------------------------------------------
void WaveformGeneratorFP::set_chip_model(chip_model model) {
	if (model == MOS6581FP) {
		wave__ST = wave6581__ST;
		wave_P_T = wave6581_P_T;
		wave_PS_ = wave6581_PS_;
		wave_PST = wave6581_PST;
	} else {
		wave__ST = wave8580__ST;
		wave_P_T = wave8580_P_T;
		wave_PS_ = wave8580_PS_;
		wave_PST = wave8580_PST;
	}
}

// ----------------------------------------------------------------------------
// Register functions.
// ----------------------------------------------------------------------------
void WaveformGeneratorFP::writeFREQ_LO(reg8 freq_lo) {
	freq = (freq & 0xff00) | (freq_lo & 0x00ff);
}

void WaveformGeneratorFP::writeFREQ_HI(reg8 freq_hi) {
	freq = ((freq_hi << 8) & 0xff00) | (freq & 0x00ff);
}

/* The original form was (acc >> 12) >= pw, where truth value is not affected
 * by the contents of the low 12 bits. Therefore the lowest bits must be zero
 * in the new formulation acc >= (pw << 12). */
void WaveformGeneratorFP::writePW_LO(reg8 pw_lo) {
	pw = (pw & 0xf00) | (pw_lo & 0x0ff);
	pw_acc_scale = pw << 12;
}

void WaveformGeneratorFP::writePW_HI(reg8 pw_hi) {
	pw = ((pw_hi << 8) & 0xf00) | (pw & 0x0ff);
	pw_acc_scale = pw << 12;
}

void WaveformGeneratorFP::writeCONTROL_REG(reg8 control) {
	waveform = (control >> 4) & 0x0f;
	ring_mod = control & 0x04;
	sync = control & 0x02;

	reg8 test_next = control & 0x08;

	/* SounDemoN found out that test bit can be used to control the noise
	 * register. Hear the result in Bojojoing.sid. */

	// testbit set. invert bit 19 and write it to bit 1
	if (test_next && !test) {
		accumulator = 0;
		reg24 bit19 = (shift_register >> 19) & 1;
		shift_register = (shift_register & 0x7ffffd) | ((bit19 ^ 1) << 1);
		noise_overwrite_delay = 200000; /* 200 ms, probably too generous? */
	}
		// Test bit cleared.
		// The accumulator starts counting, and the shift register is reset to
		// the value 0x7ffff8.
	else if (!test_next && test) {
		reg24 bit0 = ((shift_register >> 22) ^ (shift_register >> 17)) & 0x1;
		shift_register <<= 1;
		shift_register |= bit0;
	}
	// clear output bits of shift register if noise and other waveforms
	// are selected simultaneously
	if (waveform > 8) {
		shift_register &= 0x7fffff ^ (1 << 22) ^ (1 << 20) ^ (1 << 16) ^ (1 << 13) ^ (1 << 11) ^ (1 << 7) ^ (1 << 4) ^ (1 << 2);
	}

	test = test_next;

	/* update noise anyway, just in case the above paths triggered */
	noise_output_cached = outputN___();
}

reg8 WaveformGeneratorFP::readOSC() {
	return output() >> 4;
}

// ----------------------------------------------------------------------------
// SID reset.
// ----------------------------------------------------------------------------
void WaveformGeneratorFP::reset() {
	accumulator = 0;
	previous = 0;
	shift_register = 0x7ffffc;
	freq = 0;
	pw = 0;
	pw_acc_scale = 0;
	test = 0;
	writeCONTROL_REG(0);
	msb_rising = false;
}
