// 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
***********************************************************/
#include "emu.h"
#include "astrocde.h"
// device type definition
const device_type ASTROCADE = &device_creator<astrocade_device>;
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// astrocade_device - constructor
//-------------------------------------------------
astrocade_device::astrocade_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, ASTROCADE, "Astrocade", tag, owner, clock, "astrocade", __FILE__),
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)
{
memset(m_reg, 0, sizeof(UINT8)*8);
memset(m_bitswap, 0, sizeof(UINT8)*256);
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void astrocade_device::device_start()
{
int i;
/* generate a bitswap table for the noise */
for (i = 0; i < 256; i++)
m_bitswap[i] = BITSWAP8(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_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
stream_sample_t *dest = outputs[0];
UINT16 noise_state;
UINT8 master_count;
UINT8 noise_clock;
/* load some locals */
master_count = m_master_count;
noise_clock = m_noise_clock;
noise_state = m_noise_state;
/* loop over samples */
while (samples > 0)
{
stream_sample_t cursample = 0;
int samples_this_time;
int samp;
/* compute the number of cycles until the next master oscillator reset */
/* or until the next noise boundary */
samples_this_time = MIN(samples, 256 - master_count);
samples_this_time = MIN(samples_this_time, 64 - noise_clock);
samples -= samples_this_time;
/* 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 */
cursample = cursample * 32767 / 60;
for (samp = 0; samp < samples_this_time; samp++)
*dest++ = cursample;
/* 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_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_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
*
*************************************/
WRITE8_MEMBER( astrocade_device::astrocade_sound_w )
{
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;
}