274 lines
6.5 KiB
C
274 lines
6.5 KiB
C
|
/*
|
||
|
|
|
||
|
|
============================================================================
|
||
|
|
|
||
|
|
SM8521 sound emulator
|
||
|
|
by cam900
|
||
|
|
|
||
|
|
This file is licensed under zlib license.
|
||
|
|
|
||
|
|
============================================================================
|
||
|
|
|
||
|
|
zlib License
|
||
|
|
|
||
|
|
(C) 2022-present cam900 and contributors
|
||
|
|
|
||
|
|
This software is provided 'as-is', without any express or implied
|
||
|
|
warranty. In no event will the authors be held liable for any damages
|
||
|
|
arising from the use of this software.
|
||
|
|
|
||
|
|
Permission is granted to anyone to use this software for any purpose,
|
||
|
|
including commercial applications, and to alter it and redistribute it
|
||
|
|
freely, subject to the following restrictions:
|
||
|
|
|
||
|
|
1. The origin of this software must not be misrepresented; you must not
|
||
|
|
claim that you wrote the original software. If you use this software
|
||
|
|
in a product, an acknowledgment in the product documentation would be
|
||
|
|
appreciated but is not required.
|
||
|
|
2. Altered source versions must be plainly marked as such, and must not be
|
||
|
|
misrepresented as being the original software.
|
||
|
|
3. This notice may not be removed or altered from any source distribution.
|
||
|
|
|
||
|
|
============================================================================
|
||
|
|
|
||
|
|
TODO:
|
||
|
|
- needs hardware test
|
||
|
|
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <stdlib.h>
|
||
|
|
|
||
|
|
#ifdef __cplusplus
|
||
|
|
extern "C"
|
||
|
|
{
|
||
|
|
#endif
|
||
|
|
|
||
|
|
enum sm8521_sgc
|
||
|
|
{
|
||
|
|
SM8521_SGC_SONDOUT = (1 << 7),
|
||
|
|
SM8521_SGC_DIROUT = (1 << 3),
|
||
|
|
SM8521_SGC_SG2OUT = (1 << 2),
|
||
|
|
SM8521_SGC_SG1OUT = (1 << 1),
|
||
|
|
SM8521_SGC_SG0OUT = (1 << 0)
|
||
|
|
};
|
||
|
|
|
||
|
|
struct sm8521_sg_t
|
||
|
|
{
|
||
|
|
unsigned short t; // Time constant register
|
||
|
|
unsigned char level; // Output level control register
|
||
|
|
unsigned short out; // output
|
||
|
|
int counter; // clock counter
|
||
|
|
};
|
||
|
|
|
||
|
|
struct sm8521_wave_t
|
||
|
|
{
|
||
|
|
struct sm8521_sg_t base;
|
||
|
|
unsigned char addr; // waveform address
|
||
|
|
unsigned char wave[16]; // 4 bit waveform (32 nybbles)
|
||
|
|
};
|
||
|
|
|
||
|
|
struct sm8521_noise_t
|
||
|
|
{
|
||
|
|
struct sm8521_sg_t base;
|
||
|
|
unsigned int lfsr; // LFSR
|
||
|
|
};
|
||
|
|
|
||
|
|
struct sm8521_t
|
||
|
|
{
|
||
|
|
struct sm8521_wave_t sg[2];
|
||
|
|
struct sm8521_noise_t noise;
|
||
|
|
signed short out; // output
|
||
|
|
signed char sgda; // D/A direct output register (write only)
|
||
|
|
unsigned char sgc; // Control register
|
||
|
|
};
|
||
|
|
|
||
|
|
void sm8521_sg_wave_tick(struct sm8521_wave_t *sg, const int cycle)
|
||
|
|
{
|
||
|
|
sg->base.counter += cycle;
|
||
|
|
while (sg->base.counter >= (sg->base.t + 1))
|
||
|
|
{
|
||
|
|
sg->addr++;
|
||
|
|
sg->base.counter -= (sg->base.t + 1);
|
||
|
|
}
|
||
|
|
int wave = (sg->wave[(sg->addr >> 1) & 0xf] >> ((sg->addr & 1) << 2)) & 0xf;
|
||
|
|
if (wave & 0x8)
|
||
|
|
{
|
||
|
|
wave = -(0x8 - (wave & 0x7));
|
||
|
|
}
|
||
|
|
sg->base.out = (wave * sg->base.level) >> 1; // scale out to 8bit
|
||
|
|
}
|
||
|
|
|
||
|
|
void sm8521_noise_tick(struct sm8521_noise_t *noise, const int cycle)
|
||
|
|
{
|
||
|
|
noise->base.counter += cycle;
|
||
|
|
while (noise->base.counter >= (noise->base.t + 1))
|
||
|
|
{
|
||
|
|
noise->lfsr = rand() & 0x1; // unknown algorithm
|
||
|
|
noise->base.counter -= (noise->base.t + 1);
|
||
|
|
}
|
||
|
|
noise->base.out = (((noise->lfsr & 0x1) ? 7 : -8) * noise->base.level) >> 1; // scale out to 8bit
|
||
|
|
}
|
||
|
|
|
||
|
|
void sm8521_sound_tick(struct sm8521_t *sm8521, const int cycle)
|
||
|
|
{
|
||
|
|
int out = 0;
|
||
|
|
if (sm8521->sgc & SM8521_SGC_SONDOUT)
|
||
|
|
{
|
||
|
|
if (sm8521->sgc & SM8521_SGC_DIROUT)
|
||
|
|
{
|
||
|
|
out = sm8521->sgda - 0x80;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
if (sm8521->sgc & SM8521_SGC_SG0OUT)
|
||
|
|
{
|
||
|
|
sm8521_sg_wave_tick(&sm8521->sg[0], cycle);
|
||
|
|
out += sm8521->sg[0].base.out;
|
||
|
|
}
|
||
|
|
if (sm8521->sgc & SM8521_SGC_SG1OUT)
|
||
|
|
{
|
||
|
|
sm8521_sg_wave_tick(&sm8521->sg[1], cycle);
|
||
|
|
out += sm8521->sg[1].base.out;
|
||
|
|
}
|
||
|
|
if (sm8521->sgc & SM8521_SGC_SG2OUT)
|
||
|
|
{
|
||
|
|
sm8521_noise_tick(&sm8521->noise, cycle);
|
||
|
|
out += sm8521->noise.base.out;
|
||
|
|
}
|
||
|
|
out = (out < -0x80) ? -0x80 : ((out > 0x7f) ? 0x7f : out); // clamp
|
||
|
|
}
|
||
|
|
}
|
||
|
|
sm8521->out = out;
|
||
|
|
}
|
||
|
|
|
||
|
|
void sm8521_reset(struct sm8521_t *sm8521)
|
||
|
|
{
|
||
|
|
for (int i = 0; i < 2; i++)
|
||
|
|
{
|
||
|
|
sm8521->sg[i].base.t = 0;
|
||
|
|
sm8521->sg[i].base.level = 0;
|
||
|
|
sm8521->sg[i].base.out = 0;
|
||
|
|
sm8521->sg[i].base.counter = 0;
|
||
|
|
sm8521->sg[i].addr = 0;
|
||
|
|
for (int j = 0; j < 16; j++)
|
||
|
|
{
|
||
|
|
sm8521->sg[i].wave[j] = 0;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
sm8521->noise.base.t = 0;
|
||
|
|
sm8521->noise.base.level = 0;
|
||
|
|
sm8521->noise.base.out = 0;
|
||
|
|
sm8521->noise.base.counter = 0;
|
||
|
|
sm8521->noise.lfsr = 0;
|
||
|
|
sm8521->out = 0;
|
||
|
|
sm8521->sgda = 0;
|
||
|
|
sm8521->sgc = 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
unsigned char sm8521_read(struct sm8521_t *sm8521, const unsigned char a)
|
||
|
|
{
|
||
|
|
if ((a & 0xe0) == 0x60)
|
||
|
|
{
|
||
|
|
if ((a & 0x10) && (!(sm8521->sgc & SM8521_SGC_SG1OUT))) // 0x70-0x7f SG1W0-15
|
||
|
|
{
|
||
|
|
return sm8521->sg[1].wave[a & 0xf];
|
||
|
|
}
|
||
|
|
else if ((!(a & 0x10)) && (!(sm8521->sgc & SM8521_SGC_SG0OUT))) // 0x60-0x6f SG0W0-15
|
||
|
|
{
|
||
|
|
return sm8521->sg[0].wave[a & 0xf];
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
switch (a)
|
||
|
|
{
|
||
|
|
case 0x40: // SGC
|
||
|
|
return sm8521->sgc;
|
||
|
|
break;
|
||
|
|
case 0x42: // SG0L
|
||
|
|
return sm8521->sg[0].base.level & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x44: // SG1L
|
||
|
|
return sm8521->sg[1].base.level & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x46: // SG0TH
|
||
|
|
return (sm8521->sg[0].base.t >> 8) & 0xf;
|
||
|
|
break;
|
||
|
|
case 0x47: // SG0TL
|
||
|
|
return sm8521->sg[0].base.t & 0xff;
|
||
|
|
break;
|
||
|
|
case 0x48: // SG1TH
|
||
|
|
return (sm8521->sg[1].base.t >> 8) & 0xf;
|
||
|
|
break;
|
||
|
|
case 0x49: // SG1TL
|
||
|
|
return sm8521->sg[1].base.t & 0x0ff;
|
||
|
|
break;
|
||
|
|
case 0x4a: // SG2L
|
||
|
|
return sm8521->noise.base.level & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x4c: // SG2TH
|
||
|
|
return (sm8521->noise.base.t >> 8) & 0xf;
|
||
|
|
break;
|
||
|
|
case 0x4d: // SG2TL
|
||
|
|
return sm8521->noise.base.t & 0xff;
|
||
|
|
break;
|
||
|
|
default:
|
||
|
|
return 0;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
void sm8521_write(struct sm8521_t *sm8521, const unsigned char a, const unsigned char d)
|
||
|
|
{
|
||
|
|
if ((a & 0xe0) == 0x60)
|
||
|
|
{
|
||
|
|
if ((a & 0x10) && (!(sm8521->sgc & SM8521_SGC_SG1OUT))) // 0x70-0x7f SG1W0-15
|
||
|
|
{
|
||
|
|
sm8521->sg[1].wave[a & 0xf] = d;
|
||
|
|
}
|
||
|
|
else if ((!(a & 0x10)) && (!(sm8521->sgc & SM8521_SGC_SG0OUT))) // 0x60-0x6f SG0W0-15
|
||
|
|
{
|
||
|
|
sm8521->sg[0].wave[a & 0xf] = d;
|
||
|
|
}
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
switch (a)
|
||
|
|
{
|
||
|
|
case 0x40: // SGC
|
||
|
|
sm8521->sgc = d;
|
||
|
|
break;
|
||
|
|
case 0x42: // SG0L
|
||
|
|
sm8521->sg[0].base.level = d & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x44: // SG1L
|
||
|
|
sm8521->sg[1].base.level = d & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x46: // SG0TH
|
||
|
|
sm8521->sg[0].base.t = (sm8521->sg[0].base.t & 0x0ff) | ((d << 8) & 0xf00);
|
||
|
|
break;
|
||
|
|
case 0x47: // SG0TL
|
||
|
|
sm8521->sg[0].base.t = (sm8521->sg[0].base.t & 0xf00) | (d & 0x0ff);
|
||
|
|
break;
|
||
|
|
case 0x48: // SG1TH
|
||
|
|
sm8521->sg[1].base.t = (sm8521->sg[1].base.t & 0x0ff) | ((d << 8) & 0xf00);
|
||
|
|
break;
|
||
|
|
case 0x49: // SG1TL
|
||
|
|
sm8521->sg[1].base.t = (sm8521->sg[1].base.t & 0xf00) | (d & 0x0ff);
|
||
|
|
break;
|
||
|
|
case 0x4a: // SG2L
|
||
|
|
sm8521->noise.base.level = d & 0x1f;
|
||
|
|
break;
|
||
|
|
case 0x4c: // SG2TH
|
||
|
|
sm8521->noise.base.t = (sm8521->noise.base.t & 0x0ff) | ((d << 8) & 0xf00);
|
||
|
|
break;
|
||
|
|
case 0x4d: // SG2TL
|
||
|
|
sm8521->noise.base.t = (sm8521->noise.base.t & 0xf00) | (d & 0x0ff);
|
||
|
|
break;
|
||
|
|
case 0x4e: // SGDA
|
||
|
|
sm8521->sgda = d;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#ifdef __cplusplus
|
||
|
|
} // extern "C"
|
||
|
|
#endif
|