// license:BSD-3-Clause
// copyright-holders:Acho A. Tang,R. Belmont
/*********************************************************
Irem GA20 PCM Sound Chip
It's not currently known whether this chip is stereo.
Revisions:
04-15-2002 Acho A. Tang
- rewrote channel mixing
- added prelimenary volume and sample rate emulation
05-30-2002 Acho A. Tang
- applied hyperbolic gain control to volume and used
a musical-note style progression in sample rate
calculation(still very inaccurate)
02-18-2004 R. Belmont
- sample rate calculation reverse-engineered.
Thanks to Fujix, Yasuhiro Ogawa, the Guru, and Tormod
for real PCB samples that made this possible.
02-03-2007 R. Belmont
- Cleaned up faux x86 assembly.
*********************************************************/
#include "emu.h"
#include "iremga20.h"
#include <algorithm>
#define MAX_VOL 256
// device type definition
DEFINE_DEVICE_TYPE(IREMGA20, iremga20_device, "iremga20", "Irem GA20")
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// iremga20_device - constructor
//-------------------------------------------------
iremga20_device::iremga20_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
device_t(mconfig, IREMGA20, tag, owner, clock),
device_sound_interface(mconfig, *this),
device_rom_interface(mconfig, *this, 20),
m_stream(nullptr)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void iremga20_device::device_start()
{
int i;
iremga20_reset();
std::fill(std::begin(m_regs), std::end(m_regs), 0);
m_stream = stream_alloc(0, 2, clock()/4);
save_item(NAME(m_regs));
for (i = 0; i < 4; i++)
{
save_item(NAME(m_channel[i].rate), i);
save_item(NAME(m_channel[i].size), i);
save_item(NAME(m_channel[i].start), i);
save_item(NAME(m_channel[i].pos), i);
save_item(NAME(m_channel[i].frac), i);
save_item(NAME(m_channel[i].end), i);
save_item(NAME(m_channel[i].volume), i);
save_item(NAME(m_channel[i].pan), i);
save_item(NAME(m_channel[i].effect), i);
save_item(NAME(m_channel[i].play), i);
}
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void iremga20_device::device_reset()
{
iremga20_reset();
}
//-------------------------------------------------
// device_clock_changed - called if the clock
// changes
//-------------------------------------------------
void iremga20_device::device_clock_changed()
{
m_stream->set_sample_rate(clock()/4);
}
//-------------------------------------------------
// rom_bank_updated - the rom bank has changed
//-------------------------------------------------
void iremga20_device::rom_bank_updated()
{
m_stream->update();
}
//-------------------------------------------------
// sound_stream_update - handle a stream update
//-------------------------------------------------
void iremga20_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
uint32_t rate[4], pos[4], frac[4], end[4], vol[4], play[4];
stream_sample_t *outL, *outR;
int i, sampleout;
/* precache some values */
for (i=0; i < 4; i++)
{
rate[i] = m_channel[i].rate;
pos[i] = m_channel[i].pos;
frac[i] = m_channel[i].frac;
end[i] = m_channel[i].end - 0x20;
vol[i] = m_channel[i].volume;
play[i] = m_channel[i].play;
}
i = samples;
outL = outputs[0];
outR = outputs[1];
for (i = 0; i < samples; i++)
{
sampleout = 0;
// update the 4 channels inline
if (play[0])
{
sampleout += (read_byte(pos[0]) - 0x80) * vol[0];
frac[0] += rate[0];
pos[0] += frac[0] >> 24;
frac[0] &= 0xffffff;
play[0] = (pos[0] < end[0]);
}
if (play[1])
{
sampleout += (read_byte(pos[1]) - 0x80) * vol[1];
frac[1] += rate[1];
pos[1] += frac[1] >> 24;
frac[1] &= 0xffffff;
play[1] = (pos[1] < end[1]);
}
if (play[2])
{
sampleout += (read_byte(pos[2]) - 0x80) * vol[2];
frac[2] += rate[2];
pos[2] += frac[2] >> 24;
frac[2] &= 0xffffff;
play[2] = (pos[2] < end[2]);
}
if (play[3])
{
sampleout += (read_byte(pos[3]) - 0x80) * vol[3];
frac[3] += rate[3];
pos[3] += frac[3] >> 24;
frac[3] &= 0xffffff;
play[3] = (pos[3] < end[3]);
}
sampleout >>= 2;
outL[i] = sampleout;
outR[i] = sampleout;
}
/* update the regs now */
for (i=0; i < 4; i++)
{
m_channel[i].pos = pos[i];
m_channel[i].frac = frac[i];
m_channel[i].play = play[i];
}
}
WRITE8_MEMBER( iremga20_device::irem_ga20_w )
{
int channel;
//logerror("GA20: Offset %02x, data %04x\n",offset,data);
m_stream->update();
channel = offset >> 3;
m_regs[offset] = data;
switch (offset & 0x7)
{
case 0: /* start address low */
m_channel[channel].start = ((m_channel[channel].start)&0xff000) | (data<<4);
break;
case 1: /* start address high */
m_channel[channel].start = ((m_channel[channel].start)&0x00ff0) | (data<<12);
break;
case 2: /* end address low */
m_channel[channel].end = ((m_channel[channel].end)&0xff000) | (data<<4);
break;
case 3: /* end address high */
m_channel[channel].end = ((m_channel[channel].end)&0x00ff0) | (data<<12);
break;
case 4:
m_channel[channel].rate = 0x1000000 / (256 - data);
break;
case 5: //AT: gain control
m_channel[channel].volume = (data * MAX_VOL) / (data + 10);
break;
case 6: //AT: this is always written 2(enabling both channels?)
m_channel[channel].play = data;
m_channel[channel].pos = m_channel[channel].start;
m_channel[channel].frac = 0;
break;
}
}
READ8_MEMBER( iremga20_device::irem_ga20_r )
{
int channel;
m_stream->update();
channel = offset >> 3;
switch (offset & 0x7)
{
case 7: // voice status. bit 0 is 1 if active. (routine around 0xccc in rtypeleo)
return m_channel[channel].play ? 1 : 0;
default:
logerror("GA20: read unk. register %d, channel %d\n", offset & 0xf, channel);
break;
}
return 0;
}
void iremga20_device::iremga20_reset()
{
int i;
for( i = 0; i < 4; i++ ) {
m_channel[i].rate = 0;
m_channel[i].size = 0;
m_channel[i].start = 0;
m_channel[i].pos = 0;
m_channel[i].frac = 0;
m_channel[i].end = 0;
m_channel[i].volume = 0;
m_channel[i].pan = 0;
m_channel[i].effect = 0;
m_channel[i].play = 0;
}
}