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/*
Copyright 2013 Michael Pavone
This file is part of BlastEm.
BlastEm is free software distributed under the terms of the GNU General Public License version 3 or greater. See COPYING for full license text.
*/
#include "psg.h"
#include "blastem.h"
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
void psg_init(psg_context * context, uint32_t master_clock, uint32_t clock_div)
{
memset(context, 0, sizeof(*context));
context->audio = render_audio_source(master_clock, clock_div, 1);
context->clock_inc = clock_div;
for (int i = 0; i < 4; i++) {
context->volume[i] = 0xF;
}
}
void psg_free(psg_context *context)
{
render_free_source(context->audio);
free(context);
}
void psg_adjust_master_clock(psg_context * context, uint32_t master_clock)
{
render_audio_adjust_clock(context->audio, master_clock, context->clock_inc);
}
void psg_write(psg_context * context, uint8_t value)
{
if (context->vgm) {
vgm_sn76489_write(context->vgm, context->cycles, value);
}
if (value & 0x80) {
context->latch = value & 0x70;
uint8_t channel = value >> 5 & 0x3;
if (value & 0x10) {
context->volume[channel] = value & 0xF;
} else {
if (channel == 3) {
switch(value & 0x3)
{
case 0:
case 1:
case 2:
context->counter_load[3] = 0x10 << (value & 0x3);
context->noise_use_tone = 0;
break;
default:
context->counter_load[3] = context->counter_load[2];
context->noise_use_tone = 1;
}
context->noise_type = value & 0x4;
context->lsfr = 0x8000;
} else {
context->counter_load[channel] = (context->counter_load[channel] & 0x3F0) | (value & 0xF);
if (channel == 2 && context->noise_use_tone) {
context->counter_load[3] = context->counter_load[2];
}
}
}
} else {
if (!(context->latch & 0x10)) {
uint8_t channel = context->latch >> 5 & 0x3;
if (channel != 3) {
context->counter_load[channel] = (value << 4 & 0x3F0) | (context->counter_load[channel] & 0xF);
if (channel == 2 && context->noise_use_tone) {
context->counter_load[3] = context->counter_load[2];
}
}
}
}
}
#define PSG_VOL_DIV 14
//table shamelessly swiped from PSG doc from smspower.org
static int16_t volume_table[16] = {
32767/PSG_VOL_DIV, 26028/PSG_VOL_DIV, 20675/PSG_VOL_DIV, 16422/PSG_VOL_DIV, 13045/PSG_VOL_DIV, 10362/PSG_VOL_DIV,
8231/PSG_VOL_DIV, 6568/PSG_VOL_DIV, 5193/PSG_VOL_DIV, 4125/PSG_VOL_DIV, 3277/PSG_VOL_DIV, 2603/PSG_VOL_DIV,
2067/PSG_VOL_DIV, 1642/PSG_VOL_DIV, 1304/PSG_VOL_DIV, 0
};
void psg_run(psg_context * context, uint32_t cycles)
{
while (context->cycles < cycles) {
for (int i = 0; i < 4; i++) {
if (context->counters[i]) {
context->counters[i] -= 1;
}
if (!context->counters[i]) {
context->counters[i] = context->counter_load[i];
context->output_state[i] = !context->output_state[i];
if (i == 3 && context->output_state[i]) {
context->noise_out = context->lsfr & 1;
context->lsfr = (context->lsfr >> 1) | (context->lsfr << 15);
if (context->noise_type) {
//white noise
if (context->lsfr & 0x40) {
context->lsfr ^= 0x8000;
}
}
}
}
}
int16_t accum = 0;
for (int i = 0; i < 3; i++) {
if (context->output_state[i]) {
accum += volume_table[context->volume[i]];
}
}
if (context->noise_out) {
accum += volume_table[context->volume[3]];
}
render_put_mono_sample(context->audio, accum);
context->cycles += context->clock_inc;
}
}
void psg_vgm_log(psg_context *context, uint32_t master_clock, vgm_writer *vgm)
{
vgm_sn76489_init(vgm, 16 * master_clock / context->clock_inc, 9, 16, 0);
context->vgm = vgm;
for (int chan = 0; chan < 4; chan++)
{
uint8_t base = chan << 5 | 0x80;
vgm_sn76489_write(context->vgm, context->cycles, context->volume[chan] | base | 0x10);
if (chan == 3) {
if (context->noise_use_tone) {
vgm_sn76489_write(context->vgm, context->cycles, 3 | base);
} else {
//0x10 = 0
//0x20 = 1
//0x40 = 2
vgm_sn76489_write(context->vgm, context->cycles, context->counter_load[chan] >> 5 | base);
}
} else {
vgm_sn76489_write(context->vgm, context->cycles, (context->counter_load[chan] & 0xF) | base);
vgm_sn76489_write(context->vgm, context->cycles, context->counter_load[chan] >> 4 & 0x3F);
}
}
}
void psg_serialize(psg_context *context, serialize_buffer *buf)
{
save_int16(buf, context->lsfr);
save_buffer16(buf, context->counter_load, 4);
save_buffer16(buf, context->counters, 4);
save_buffer8(buf, context->volume, 4);
uint8_t output_state = context->output_state[0] << 3 | context->output_state[1] << 2
| context->output_state[2] << 1 | context->output_state[3]
| context->noise_use_tone << 4;
save_int8(buf, output_state);
save_int8(buf, context->noise_type);
save_int8(buf, context->latch);
save_int32(buf, context->cycles);
}
void psg_deserialize(deserialize_buffer *buf, void *vcontext)
{
psg_context *context = vcontext;
context->lsfr = load_int16(buf);
load_buffer16(buf, context->counter_load, 4);
load_buffer16(buf, context->counters, 4);
load_buffer8(buf, context->volume, 4);
uint8_t output_state = load_int8(buf);
context->output_state[0] = output_state >> 3 & 1;
context->output_state[1] = output_state >> 2 & 1;
context->output_state[2] = output_state >> 1 & 1;
context->output_state[3] = output_state & 1;
context->noise_use_tone = output_state >> 4 & 1;
context->noise_type = load_int8(buf);
context->latch = load_int8(buf);
context->cycles = load_int32(buf);
}
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