// license:BSD-3-Clause
// copyright-holders:Aaron Giles,Frank Palazzolo
/***********************************************************

    Astrocade custom 'IO' chip sound chip driver
    Aaron Giles
    based on original work by Frank Palazzolo

************************************************************

    Register Map
    ============

    Register 0:
        D7..D0: Master oscillator frequency

    Register 1:
        D7..D0: Tone generator A frequency

    Register 2:
        D7..D0: Tone generator B frequency

    Register 3:
        D7..D0: Tone generator C frequency

    Register 4:
        D7..D6: Vibrato speed
        D5..D0: Vibrato depth

    Register 5:
            D5: Noise AM enable
            D4: Mux source (0=vibrato, 1=noise)
        D3..D0: Tone generator C volume

    Register 6:
        D7..D4: Tone generator B volume
        D3..D0: Tone generator A volume

    Register 7:
        D7..D0: Noise volume

************************************************************

    The device has active high(!) SO strobes triggered by
    read accesses, which transfer data from the 8 SI lines
    to the bus. Logically SO0-7 and SI0-7 ought to be hooked
    up to the same input matrix, but this only appears to be
    the case with the Astrocade home systems.  The arcade
    games instead channel the SI inputs through a quartet of
    MC14539B (pin-compatible with 74153) CMOS multiplexers
    and connect the SO strobes to unrelated outputs which
    generally use the upper 8 address bits as data.

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

#include "emu.h"
#include "astrocde.h"


// device type definition
DEFINE_DEVICE_TYPE(ASTROCADE_IO, astrocade_io_device, "astrocade_io", "Astrocade Custom I/O")


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

//-------------------------------------------------
//  astrocade_io_device - constructor
//-------------------------------------------------

astrocade_io_device::astrocade_io_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: device_t(mconfig, ASTROCADE_IO, tag, owner, clock)
	, device_sound_interface(mconfig, *this)
	, m_stream(nullptr)
	, m_master_count(0)
	, m_vibrato_clock(0)
	, m_noise_clock(0)
	, m_noise_state(0)
	, m_a_count(0)
	, m_a_state(0)
	, m_b_count(0)
	, m_b_state(0)
	, m_c_count(0)
	, m_c_state(0)
	, m_si_callback(*this, 0)
	, m_so_callback(*this)
	, m_pots(*this, 0)
{
	memset(m_reg, 0, sizeof(uint8_t)*8);
	memset(m_bitswap, 0, sizeof(uint8_t)*256);
}


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

void astrocade_io_device::device_start()
{
	/* generate a bitswap table for the noise */
	for (int i = 0; i < 256; i++)
		m_bitswap[i] = bitswap<8>(i, 0,1,2,3,4,5,6,7);

	/* allocate a stream for output */
	m_stream = stream_alloc(0, 1, clock());

	/* reset state */
	device_reset();
	state_save_register();
}


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

void astrocade_io_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
{
	auto &dest = outputs[0];
	uint16_t noise_state;
	uint8_t master_count;
	uint8_t noise_clock;

	/* load some locals */
	master_count = m_master_count;
	noise_clock = m_noise_clock;
	noise_state = m_noise_state;

	/* loop over samples */
	int samples_this_time;
	constexpr stream_buffer::sample_t sample_scale = 1.0f / 60.0f;
	for (int sampindex = 0; sampindex < dest.samples(); sampindex += samples_this_time)
	{
		s32 cursample = 0;

		/* compute the number of cycles until the next master oscillator reset */
		/* or until the next noise boundary */
		samples_this_time = std::min<int>(dest.samples() - sampindex, 256 - master_count);
		samples_this_time = std::min(samples_this_time, 64 - noise_clock);

		/* sum the output of the tone generators */
		if (m_a_state)
			cursample += m_reg[6] & 0x0f;
		if (m_b_state)
			cursample += m_reg[6] >> 4;
		if (m_c_state)
			cursample += m_reg[5] & 0x0f;

		/* add in the noise if it is enabled, based on the top bit of the LFSR */
		if ((m_reg[5] & 0x20) && (noise_state & 0x4000))
			cursample += m_reg[7] >> 4;

		/* scale to max and output */
		dest.fill(stream_buffer::sample_t(cursample) * sample_scale, sampindex, samples_this_time);

		/* clock the noise; a 2-bit counter clocks a 4-bit counter which clocks the LFSR */
		noise_clock += samples_this_time;
		if (noise_clock >= 64)
		{
			/* update the noise state; this is a 15-bit LFSR with feedback from */
			/* the XOR of the top two bits */
			noise_state = (noise_state << 1) | (~((noise_state >> 14) ^ (noise_state >> 13)) & 1);
			noise_clock -= 64;

			/* the same clock also controls the vibrato clock, which is a 13-bit counter */
			m_vibrato_clock++;
		}

		/* clock the master oscillator; this is an 8-bit up counter */
		master_count += samples_this_time;
		if (master_count == 0)
		{
			/* reload based on mux value -- the value from the register is negative logic */
			master_count = ~m_reg[0];

			/* mux value 0 means reload based on the vibrato control */
			if ((m_reg[5] & 0x10) == 0)
			{
				/* vibrato speed (register 4 bits 6-7) selects one of the top 4 bits */
				/* of the 13-bit vibrato clock to use (0=highest freq, 3=lowest) */
				if (!((m_vibrato_clock >> (m_reg[4] >> 6)) & 0x0200))
				{
					/* if the bit is clear, we add the vibrato volume to the counter */
					master_count += m_reg[4] & 0x3f;
				}
			}

			/* mux value 1 means reload based on the noise control */
			else
			{
				/* the top 8 bits of the noise LFSR are ANDed with the noise volume */
				/* register and added to the count */
				master_count += m_bitswap[(noise_state >> 7) & 0xff] & m_reg[7];
			}

			/* clock tone A */
			if (++m_a_count == 0)
			{
				m_a_state ^= 1;
				m_a_count = ~m_reg[1];
			}

			/* clock tone B */
			if (++m_b_count == 0)
			{
				m_b_state ^= 1;
				m_b_count = ~m_reg[2];
			}

			/* clock tone C */
			if (++m_c_count == 0)
			{
				m_c_state ^= 1;
				m_c_count = ~m_reg[3];
			}
		}
	}

	/* put back the locals */
	m_master_count = master_count;
	m_noise_clock = noise_clock;
	m_noise_state = noise_state;
}


//-------------------------------------------------
//  device_reset - device-specific reset
//-------------------------------------------------

void astrocade_io_device::device_reset()
{
	memset(m_reg, 0, sizeof(m_reg));

	m_master_count = 0;
	m_vibrato_clock = 0;

	m_noise_clock = 0;
	m_noise_state = 0;

	m_a_count = 0;
	m_a_state = 0;

	m_b_count = 0;
	m_b_state = 0;

	m_c_count = 0;
	m_c_state = 0;
}


//-------------------------------------------------
//  Save state registration
//-------------------------------------------------

void astrocade_io_device::state_save_register()
{
	save_item(NAME(m_reg));

	save_item(NAME(m_master_count));
	save_item(NAME(m_vibrato_clock));

	save_item(NAME(m_noise_clock));
	save_item(NAME(m_noise_state));

	save_item(NAME(m_a_count));
	save_item(NAME(m_a_state));

	save_item(NAME(m_b_count));
	save_item(NAME(m_b_state));

	save_item(NAME(m_c_count));
	save_item(NAME(m_c_state));
}


/*************************************
 *
 *  Sound write accessors
 *
 *************************************/

void astrocade_io_device::write(offs_t offset, uint8_t data)
{
	if ((offset & 8) != 0)
		offset = (offset >> 8) & 7;
	else
		offset &= 7;

	/* update */
	m_stream->update();

	/* stash the new register value */
	m_reg[offset & 7] = data;
}


uint8_t astrocade_io_device::read(offs_t offset)
{
	if ((offset & 0x0f) < 0x08)
	{
		if (!machine().side_effects_disabled())
			m_so_callback[offset & 7](0, offset >> 8);

		return m_si_callback(offset & 7);
	}
	else if ((offset & 0x0f) >= 0x0c)
		return m_pots[offset & 3]();
	else
		return 0xff;
}