240 lines
6 KiB
C
240 lines
6 KiB
C
/*
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============================================================================
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SM8521 sound emulator
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by cam900
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MODIFIED BY TILDEARROW
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THIS IS NOT THE ORIGINAL VERSION
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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 "sm8521.h"
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#include <stdlib.h>
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enum sm8521_sgc
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{
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SM8521_SGC_SONDOUT = (1 << 7),
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SM8521_SGC_DIROUT = (1 << 3),
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SM8521_SGC_SG2OUT = (1 << 2),
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SM8521_SGC_SG1OUT = (1 << 1),
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SM8521_SGC_SG0OUT = (1 << 0)
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};
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void sm8521_sg_wave_tick(struct sm8521_wave_t *sg, const int cycle)
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{
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sg->base.counter += cycle;
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while (sg->base.counter >= (sg->base.t + 1))
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{
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sg->addr++;
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sg->base.counter -= (sg->base.t + 1);
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}
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int wave = (sg->wave[(sg->addr >> 1) & 0xf] >> ((sg->addr & 1) << 2)) & 0xf;
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if (wave & 0x8)
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{
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wave = -(0x8 - (wave & 0x7));
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}
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sg->base.out = (wave * sg->base.level) >> 1; // scale out to 8bit
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}
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void sm8521_noise_tick(struct sm8521_noise_t *noise, const int cycle)
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{
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noise->base.counter += cycle;
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while (noise->base.counter >= (noise->base.t + 1))
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{
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// unknown algorithm, but don't use rand()
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noise->lfsr = ( noise->lfsr>>1|(((noise->lfsr) ^ (noise->lfsr >> 5) ^ (noise->lfsr >> 8) ^ (noise->lfsr >> 13) ) & 1)<<31);
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noise->base.counter -= (noise->base.t + 1);
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}
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noise->base.out = (((noise->lfsr & 0x1) ? 7 : -8) * noise->base.level) >> 1; // scale out to 8bit
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}
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void sm8521_sound_tick(struct sm8521_t *sm8521, const int cycle)
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{
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int out = 0;
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if (sm8521->sgc & SM8521_SGC_SONDOUT)
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{
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if (sm8521->sgc & SM8521_SGC_DIROUT)
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{
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out = sm8521->sgda - 0x80;
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}
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else
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{
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if (sm8521->sgc & SM8521_SGC_SG0OUT)
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{
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sm8521_sg_wave_tick(&sm8521->sg[0], cycle);
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out += sm8521->sg[0].base.out;
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}
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if (sm8521->sgc & SM8521_SGC_SG1OUT)
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{
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sm8521_sg_wave_tick(&sm8521->sg[1], cycle);
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out += sm8521->sg[1].base.out;
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}
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if (sm8521->sgc & SM8521_SGC_SG2OUT)
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{
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sm8521_noise_tick(&sm8521->noise, cycle);
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out += sm8521->noise.base.out;
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}
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out = (out < -0x80) ? -0x80 : ((out > 0x7f) ? 0x7f : out); // clamp
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}
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}
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sm8521->out = out;
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}
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void sm8521_reset(struct sm8521_t *sm8521)
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{
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for (int i = 0; i < 2; i++)
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{
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sm8521->sg[i].base.t = 0;
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sm8521->sg[i].base.level = 0;
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sm8521->sg[i].base.out = 0;
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sm8521->sg[i].base.counter = 0;
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sm8521->sg[i].addr = 0;
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for (int j = 0; j < 16; j++)
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{
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sm8521->sg[i].wave[j] = 0;
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}
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}
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sm8521->noise.base.t = 0;
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sm8521->noise.base.level = 0;
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sm8521->noise.base.out = 0;
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sm8521->noise.base.counter = 0;
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sm8521->noise.lfsr = 0x89abcdef;
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sm8521->out = 0;
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sm8521->sgda = 0;
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sm8521->sgc = 0;
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}
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unsigned char sm8521_read(struct sm8521_t *sm8521, const unsigned char a)
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{
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if ((a & 0xe0) == 0x60)
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{
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if ((a & 0x10) && (!(sm8521->sgc & SM8521_SGC_SG1OUT))) // 0x70-0x7f SG1W0-15
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{
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return sm8521->sg[1].wave[a & 0xf];
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}
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else if ((!(a & 0x10)) && (!(sm8521->sgc & SM8521_SGC_SG0OUT))) // 0x60-0x6f SG0W0-15
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{
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return sm8521->sg[0].wave[a & 0xf];
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}
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return 0;
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}
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switch (a)
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{
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case 0x40: // SGC
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return sm8521->sgc;
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break;
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case 0x42: // SG0L
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return sm8521->sg[0].base.level & 0x1f;
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break;
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case 0x44: // SG1L
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return sm8521->sg[1].base.level & 0x1f;
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break;
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case 0x46: // SG0TH
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return (sm8521->sg[0].base.t >> 8) & 0xf;
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break;
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case 0x47: // SG0TL
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return sm8521->sg[0].base.t & 0xff;
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break;
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case 0x48: // SG1TH
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return (sm8521->sg[1].base.t >> 8) & 0xf;
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break;
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case 0x49: // SG1TL
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return sm8521->sg[1].base.t & 0x0ff;
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break;
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case 0x4a: // SG2L
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return sm8521->noise.base.level & 0x1f;
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break;
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case 0x4c: // SG2TH
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return (sm8521->noise.base.t >> 8) & 0xf;
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break;
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case 0x4d: // SG2TL
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return sm8521->noise.base.t & 0xff;
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break;
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default:
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return 0;
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break;
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}
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}
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void sm8521_write(struct sm8521_t *sm8521, const unsigned char a, const unsigned char d)
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{
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if ((a & 0xe0) == 0x60)
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{
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if ((a & 0x10) && (!(sm8521->sgc & SM8521_SGC_SG1OUT))) // 0x70-0x7f SG1W0-15
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{
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sm8521->sg[1].wave[a & 0xf] = d;
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}
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else if ((!(a & 0x10)) && (!(sm8521->sgc & SM8521_SGC_SG0OUT))) // 0x60-0x6f SG0W0-15
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{
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sm8521->sg[0].wave[a & 0xf] = d;
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}
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return;
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}
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switch (a)
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{
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case 0x40: // SGC
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sm8521->sgc = d;
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break;
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case 0x42: // SG0L
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sm8521->sg[0].base.level = d & 0x1f;
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break;
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case 0x44: // SG1L
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sm8521->sg[1].base.level = d & 0x1f;
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break;
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case 0x46: // SG0TH
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sm8521->sg[0].base.t = (sm8521->sg[0].base.t & 0x0ff) | ((d << 8) & 0xf00);
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break;
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case 0x47: // SG0TL
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sm8521->sg[0].base.t = (sm8521->sg[0].base.t & 0xf00) | (d & 0x0ff);
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break;
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case 0x48: // SG1TH
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sm8521->sg[1].base.t = (sm8521->sg[1].base.t & 0x0ff) | ((d << 8) & 0xf00);
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break;
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case 0x49: // SG1TL
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sm8521->sg[1].base.t = (sm8521->sg[1].base.t & 0xf00) | (d & 0x0ff);
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break;
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case 0x4a: // SG2L
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sm8521->noise.base.level = d & 0x1f;
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break;
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case 0x4c: // SG2TH
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sm8521->noise.base.t = (sm8521->noise.base.t & 0x0ff) | ((d << 8) & 0xf00);
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break;
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case 0x4d: // SG2TL
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sm8521->noise.base.t = (sm8521->noise.base.t & 0xf00) | (d & 0x0ff);
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break;
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case 0x4e: // SGDA
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sm8521->sgda = d;
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break;
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}
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}
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