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k005289.c
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C/C++ Source or Header
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2000-04-04
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242 lines
/***************************************************************************
Konami 005289 - SCC sound as used in Bubblesystem
This file is pieced together by Bryan McPhail from a combination of
Namco Sound, Amuse by Cab, Nemesis schematics and whoever first
figured out SCC!
The 005289 is a 2 channel sound generator, each channel gets it's
waveform from a prom (4 bits wide).
(From Nemesis schematics)
Address lines A0-A4 of the prom run to the 005289, giving 32 bytes
per waveform. Address lines A5-A7 of the prom run to PA5-PA7 of
the AY8910 control port A, giving 8 different waveforms. PA0-PA3
of the AY8910 control volume.
The second channel is the same as above except port B is used.
The 005289 has no data bus, so data values written don't matter.
There are 4 unknown pins, LD1, LD2, TG1, TG2. Two of them look to be
the selector for changing frequency. The other two seem unused.
***************************************************************************/
#include "driver.h"
#define FREQBASEBITS 16
/* this structure defines the parameters for a channel */
typedef struct
{
int frequency;
int counter;
int volume;
const unsigned char *wave;
} k005289_sound_channel;
static k005289_sound_channel channel_list[2];
/* global sound parameters */
static const unsigned char *sound_prom;
static int stream,mclock,rate;
/* mixer tables and internal buffers */
static INT16 *mixer_table;
static INT16 *mixer_lookup;
static short *mixer_buffer;
static int k005289_A_frequency,k005289_B_frequency;
static int k005289_A_volume,k005289_B_volume;
static int k005289_A_waveform,k005289_B_waveform;
static int k005289_A_latch,k005289_B_latch;
/* build a table to divide by the number of voices */
static int make_mixer_table(int voices)
{
int count = voices * 128;
int i;
int gain = 16;
/* allocate memory */
mixer_table = malloc(256 * voices * sizeof(INT16));
if (!mixer_table)
return 1;
/* find the middle of the table */
mixer_lookup = mixer_table + (128 * voices);
/* fill in the table - 16 bit case */
for (i = 0; i < count; i++)
{
int val = i * gain * 16 / voices;
if (val > 32767) val = 32767;
mixer_lookup[ i] = val;
mixer_lookup[-i] = -val;
}
return 0;
}
/* generate sound to the mix buffer */
static void K005289_update(int ch, INT16 *buffer, int length)
{
k005289_sound_channel *voice=channel_list;
short *mix;
int i,v,f;
/* zap the contents of the mixer buffer */
memset(mixer_buffer, 0, length * sizeof(INT16));
v=voice[0].volume;
f=voice[0].frequency;
if (v && f)
{
const unsigned char *w = voice[0].wave;
int c = voice[0].counter;
mix = mixer_buffer;
/* add our contribution */
for (i = 0; i < length; i++)
{
int offs;
c+=(long)((((float)mclock / (float)(f * 16))*(float)(1<<FREQBASEBITS)) / (float)(rate / 32));
offs = (c >> 16) & 0x1f;
*mix++ += ((w[offs] & 0x0f) - 8) * v;
}
/* update the counter for this voice */
voice[0].counter = c;
}
v=voice[1].volume;
f=voice[1].frequency;
if (v && f)
{
const unsigned char *w = voice[1].wave;
int c = voice[1].counter;
mix = mixer_buffer;
/* add our contribution */
for (i = 0; i < length; i++)
{
int offs;
c+=(long)((((float)mclock / (float)(f * 16))*(float)(1<<FREQBASEBITS)) / (float)(rate / 32));
offs = (c >> 16) & 0x1f;
*mix++ += ((w[offs] & 0x0f) - 8) * v;
}
/* update the counter for this voice */
voice[1].counter = c;
}
/* mix it down */
mix = mixer_buffer;
for (i = 0; i < length; i++)
*buffer++ = mixer_lookup[*mix++];
}
int K005289_sh_start(const struct MachineSound *msound)
{
const char *snd_name = "K005289";
k005289_sound_channel *voice=channel_list;
const struct k005289_interface *intf = msound->sound_interface;
/* get stream channels */
stream = stream_init(snd_name, intf->volume, Machine->sample_rate, 0, K005289_update);
mclock = intf->master_clock;
rate = Machine->sample_rate;
/* allocate a pair of buffers to mix into - 1 second's worth should be more than enough */
if ((mixer_buffer = malloc(2 * sizeof(short) * Machine->sample_rate)) == 0)
return 1;
/* build the mixer table */
if (make_mixer_table(2))
{
free (mixer_buffer);
return 1;
}
sound_prom = memory_region(intf->region);
/* reset all the voices */
voice[0].frequency = 0;
voice[0].volume = 0;
voice[0].wave = &sound_prom[0];
voice[0].counter = 0;
voice[1].frequency = 0;
voice[1].volume = 0;
voice[1].wave = &sound_prom[0x100];
voice[1].counter = 0;
return 0;
}
void K005289_sh_stop(void)
{
free (mixer_table);
free (mixer_buffer);
}
/********************************************************************************/
static void k005289_recompute(void)
{
k005289_sound_channel *voice = channel_list;
stream_update(stream,0); /* update the streams */
voice[0].frequency = k005289_A_frequency;
voice[1].frequency = k005289_B_frequency;
voice[0].volume = k005289_A_volume;
voice[1].volume = k005289_B_volume;
voice[0].wave = &sound_prom[32 * k005289_A_waveform];
voice[1].wave = &sound_prom[32 * k005289_B_waveform + 0x100];
}
WRITE_HANDLER( k005289_control_A_w )
{
k005289_A_volume=data&0xf;
k005289_A_waveform=data>>5;
k005289_recompute();
}
WRITE_HANDLER( k005289_control_B_w )
{
k005289_B_volume=data&0xf;
k005289_B_waveform=data>>5;
k005289_recompute();
}
WRITE_HANDLER( k005289_pitch_A_w )
{
k005289_A_latch = 0x1000 - offset;
}
WRITE_HANDLER( k005289_pitch_B_w )
{
k005289_B_latch = 0x1000 - offset;
}
WRITE_HANDLER( k005289_keylatch_A_w )
{
k005289_A_frequency = k005289_A_latch;
k005289_recompute();
}
WRITE_HANDLER( k005289_keylatch_B_w )
{
k005289_B_frequency = k005289_B_latch;
k005289_recompute();
}