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// license:BSD-3-Clause
// copyright-holders:Aaron Giles
#include "emu.h"
#include "ym2203.h"
DEFINE_DEVICE_TYPE(YM2203, ym2203_device, "ym2203", "YM2203 OPN")
//*********************************************************
// YM2203 DEVICE
//*********************************************************
//-------------------------------------------------
// ym2203_device - constructor
//-------------------------------------------------
ym2203_device::ym2203_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
ay8910_device(mconfig, YM2203, tag, owner, clock, PSG_TYPE_YM, 3, 2),
m_fm(*this),
m_stream(nullptr),
m_busy_duration(m_fm.compute_busy_duration()),
m_address(0)
{
}
//-------------------------------------------------
// read - handle a read from the device
//-------------------------------------------------
u8 ym2203_device::read(offs_t offset)
{
u8 result = 0;
switch (offset & 1)
{
case 0: // status port
result = m_fm.status();
break;
case 1: // data port (only SSG)
if (m_address < 0x10)
result = ay8910_read_ym();
break;
}
return result;
}
//-------------------------------------------------
// write - handle a write to the register
// interface
//-------------------------------------------------
void ym2203_device::write(offs_t offset, u8 value)
{
switch (offset & 1)
{
case 0: // address port
m_address = value;
if (m_address < 0x10)
{
// write register to SSG
ay8910_write_ym(0, m_address);
}
else if (m_address >= 0x2d && m_address <= 0x2f)
{
// prescaler select : 2d,2e,2f
if (m_address == 0x2d)
update_prescale(6);
else if (m_address == 0x2e && m_fm.clock_prescale() == 6)
update_prescale(3);
else if (m_address == 0x2f)
update_prescale(2);
}
break;
case 1: // data port
if (m_address < 0x10)
{
// write to SSG
ay8910_write_ym(1, value);
}
else
{
// write to FM
m_stream->update();
m_fm.write(m_address, value);
}
// mark busy for a bit
m_fm.set_busy_end(machine().time() + m_busy_duration);
break;
}
}
//-------------------------------------------------
// device_start - start of emulation
//-------------------------------------------------
void ym2203_device::device_start()
{
// start the SSG device
ay8910_device::device_start();
// create our stream
m_stream = stream_alloc(0, fm_engine::OUTPUTS, m_fm.sample_rate(clock()));
// initialize the FM engine
m_fm.init();
}
//-------------------------------------------------
// device_register_save - register for save state
//-------------------------------------------------
void ym2203_device::device_register_save(save_registrar &save)
{
// call our parent
save_registrar container(save, "psg");
ay8910_device::device_register_save(container);
// save our data
save.reg(NAME(m_address))
.reg(NAME(m_fm));
}
//-------------------------------------------------
// device_reset - start of emulation
//-------------------------------------------------
void ym2203_device::device_reset()
{
// reset the SSG device
ay8910_device::device_reset();
// reset the FM engine
m_fm.reset();
}
//-------------------------------------------------
// device_clock_changed - update if clock changes
//-------------------------------------------------
void ym2203_device::device_clock_changed()
{
// refresh via prescale
update_prescale(m_fm.clock_prescale());
}
//-------------------------------------------------
// sound_stream_update - update the sound stream
//-------------------------------------------------
void ym2203_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
{
// if this is not our stream, pass it on
if (&stream != m_stream)
{
ay8910_device::sound_stream_update(stream, inputs, outputs);
return;
}
// iterate over all target samples
for (int sampindex = 0; sampindex < outputs[0].samples(); sampindex++)
{
// clock the system
m_fm.clock(fm_engine::ALL_CHANNELS);
// update the FM content; YM2203 is full 14-bit with no intermediate clipping
s32 sums[fm_engine::OUTPUTS] = { 0 };
m_fm.output(sums, 0, 32767, fm_engine::ALL_CHANNELS);
// convert to 10.3 floating point value for the DAC and back
// YM2203 is mono
for (int index = 0; index < fm_engine::OUTPUTS; index++)
outputs[index].put_int(sampindex, ymfm_roundtrip_fp(sums[index]), 32768);
}
}
//-------------------------------------------------
// update_prescale - set a new prescale value and
// update clocks as needed
//-------------------------------------------------
void ym2203_device::update_prescale(u8 newval)
{
// inform the FM engine and refresh our clock rate
m_fm.set_clock_prescale(newval);
m_stream->set_sample_rate(m_fm.sample_rate(clock()));
logerror("Prescale = %d; sample_rate = %d\n", newval, m_fm.sample_rate(clock()));
// also scale the SSG streams
// mapping is (FM->SSG): 6->4, 3->2, 2->1
u8 ssg_scale = 2 * newval / 3;
// QUESTION: where does the *2 come from??
ay_set_clock(clock() * 2 / ssg_scale);
// recompute the busy duration
m_busy_duration = m_fm.compute_busy_duration();
}
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