87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
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/*
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============================================================================
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NEC D65010G031 sound emulator
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by cam900
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This file is licensed under zlib license.
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============================================================================
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zlib License
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(C) 2023-present cam900 and contributors
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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============================================================================
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TODO:
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- needs hardware test
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*/
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#include "d65010g031.h"
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#include <stdlib.h>
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static int d65010g031_max(int a, int b) { return (a > b) ? a : b; }
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int d65010g031_square_tick(struct d65010g031_square_t *square, const int cycle)
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{
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if (square->period > 0)
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{
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int period = d65010g031_max(1, (0x3f - square->period));
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square->counter += cycle;
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while (square->counter >= period)
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{
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square->counter -= period;
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square->out ^= 1;
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}
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return square->out;
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}
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return 0;
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}
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int d65010g031_sound_tick(struct d65010g031_t *d65010g031, const int cycle)
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{
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int out = 0;
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for (int i = 0; i < 3; i++)
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{
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out += d65010g031_square_tick(&d65010g031->square[i], cycle);
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}
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return out;
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}
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void d65010g031_reset(struct d65010g031_t *d65010g031)
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{
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for (int i = 0; i < 3; i++)
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{
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d65010g031->square[i].period = 0;
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d65010g031->square[i].counter = 0;
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d65010g031->square[i].out = 0;
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}
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}
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void d65010g031_write(struct d65010g031_t *d65010g031, const unsigned char a, const unsigned char d)
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{
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if (a < 3)
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{
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d65010g031->square[a].period = d & 0x3f;
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}
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}
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