// license:BSD-3-Clause
// copyright-holders:Bryan McPhail
/***************************************************************************

    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 its
    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 12 address inputs and 4 control inputs: LD1, LD2, TG1, TG2.
    It has no data bus, so data values written don't matter.
    When LD1 or LD2 is asserted, the 12 bit value on the address bus is
    latched. Each of the two channels has its own latch.
    When TG1 or TG2 is asserted, the frequency of the respective channel is
    set to the previously latched value.

    The 005289 itself is nothing but an address generator. Digital to analog
    conversion, volume control and mixing of the channels is all done
    externally via resistor networks and 4066 switches and is only implemented
    here for convenience.

***************************************************************************/

#include "emu.h"
#include "k005289.h"

// is this an actual hardware limit? or just an arbitrary divider
// to bring the output frequency down to a reasonable value for MAME?
#define CLOCK_DIVIDER 32

// device type definition
DEFINE_DEVICE_TYPE(K005289, k005289_device, "k005289", "K005289 SCC")


//**************************************************************************
//  LIVE DEVICE
//**************************************************************************

//-------------------------------------------------
//  k005289_device - constructor
//-------------------------------------------------

k005289_device::k005289_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: device_t(mconfig, K005289, tag, owner, clock)
	, device_sound_interface(mconfig, *this)
	, m_sound_prom(*this, DEVICE_SELF)
	, m_stream(nullptr)
	, m_rate(0)
	, m_mixer_table(nullptr)
	, m_mixer_lookup(nullptr)
	, m_mixer_buffer(nullptr)
{
}


//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

void k005289_device::device_start()
{
	/* get stream channels */
	m_rate = clock() / CLOCK_DIVIDER;
	m_stream = stream_alloc(0, 1, m_rate);

	/* allocate a pair of buffers to mix into - 1 second's worth should be more than enough */
	m_mixer_buffer = std::make_unique<short[]>(2 * m_rate);

	/* build the mixer table */
	make_mixer_table(2);

	/* reset all the voices */
	for (int i = 0; i < 2; i++)
	{
		m_counter[i] = 0;
		m_frequency[i] = 0;
		m_freq_latch[i] = 0;
		m_waveform[i] = i * 0x100;
		m_volume[i] = 0;
	}

	save_item(NAME(m_counter));
	save_item(NAME(m_frequency));
	save_item(NAME(m_freq_latch));
	save_item(NAME(m_waveform));
	save_item(NAME(m_volume));
}


//-------------------------------------------------
//  sound_stream_update - handle a stream update
//-------------------------------------------------

void k005289_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
	stream_sample_t *buffer = outputs[0];
	short *mix;
	int i,v,f;

	/* zap the contents of the mixer buffer */
	memset(m_mixer_buffer.get(), 0, samples * sizeof(int16_t));

	v=m_volume[0];
	f=m_frequency[0];
	if (v && f)
	{
		const unsigned char *w = &m_sound_prom[m_waveform[0]];
		int c = m_counter[0];

		mix = m_mixer_buffer.get();

		/* add our contribution */
		for (i = 0; i < samples; i++)
		{
			int offs;

			c += CLOCK_DIVIDER;
			offs = (c / f) & 0x1f;
			*mix++ += ((w[offs] & 0x0f) - 8) * v;
		}

		/* update the counter for this voice */
		m_counter[0] = c % (f * 0x20);
	}

	v=m_volume[1];
	f=m_frequency[1];
	if (v && f)
	{
		const unsigned char *w = &m_sound_prom[m_waveform[1]];
		int c = m_counter[1];

		mix = m_mixer_buffer.get();

		/* add our contribution */
		for (i = 0; i < samples; i++)
		{
			int offs;

			c += CLOCK_DIVIDER;
			offs = (c / f) & 0x1f;
			*mix++ += ((w[offs] & 0x0f) - 8) * v;
		}

		/* update the counter for this voice */
		m_counter[1] = c % (f * 0x20);
	}

	/* mix it down */
	mix = m_mixer_buffer.get();
	for (i = 0; i < samples; i++)
		*buffer++ = m_mixer_lookup[*mix++];
}




/********************************************************************************/

/* build a table to divide by the number of voices */
void k005289_device::make_mixer_table(int voices)
{
	int count = voices * 128;
	int i;
	int gain = 16;

	/* allocate memory */
	m_mixer_table = std::make_unique<int16_t[]>(256 * voices);

	/* find the middle of the table */
	m_mixer_lookup = m_mixer_table.get() + (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;
		m_mixer_lookup[ i] = val;
		m_mixer_lookup[-i] = -val;
	}
}


WRITE8_MEMBER( k005289_device::k005289_control_A_w )
{
	m_stream->update();

	m_volume[0] = data & 0xf;
	m_waveform[0] = data & 0xe0;
}


WRITE8_MEMBER( k005289_device::k005289_control_B_w )
{
	m_stream->update();

	m_volume[1] = data & 0xf;
	m_waveform[1] = (data & 0xe0) + 0x100;
}


WRITE8_MEMBER( k005289_device::ld1_w )
{
	m_freq_latch[0] = 0xfff - offset;
}


WRITE8_MEMBER( k005289_device::ld2_w )
{
	m_freq_latch[1] = 0xfff - offset;
}


WRITE8_MEMBER( k005289_device::tg1_w )
{
	m_stream->update();

	m_frequency[0] = m_freq_latch[0];
}


WRITE8_MEMBER( k005289_device::tg2_w )
{
	m_stream->update();

	m_frequency[1] = m_freq_latch[1];
}
