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+// license:BSD-3-Clause
+// copyright-holders:Mirko Buffoni, James Wallace
+/**********************************************************************************************
+ *
+ * OKI MSM6376 ADPCM
+ * by Mirko Buffoni, J. Wallace
+ *
+ * TODO:
+ * add BEEP tone generator
+ * confirm echo
+ * sample divisor in ROM table not implemented (no documentation)
+ * modernise
+ **********************************************************************************************/
+
+
+#include "emu.h"
+#include "okim6376.h"
+
+#define MAX_SAMPLE_CHUNK 10000
+//#define MAX_WORDS 111
+
+#define OKIVERBOSE 0
+#define MSM6376LOG(x) do { if (OKIVERBOSE) logerror x; } while (0)
+
+/* step size index shift table */
+static const int index_shift[8] = { -1, -1, -1, -1, 2, 4, 6, 8 };
+
+/* lookup table for the precomputed difference */
+static int diff_lookup[49*16];
+
+/* volume lookup table. Upon configuration, the number of ST pulses determine how much
+ attenuation to apply to the sound signal. However, this only applies to the second
+ channel*/
+static const int volume_table[3] =
+{
+ 0x20, // 0 dB
+ 0x10, // -6.0 dB
+ 0x08, // -12.0 dB
+};
+
+/* divisor lookup table. When an individual word is selected, it can be assigned one of three different 'rates'.
+ These are implemented as clock divisors, and are looked up in the ROM header. More often than not, this value is 0,
+ relating to a division by 8, or nominally 8KHz sampling (based on the datasheet example of a 64KHz clock).*/
+static const int divisor_table[3] =
+{
+ 8,
+ 10,
+ 16,
+};
+
+/* tables computed? */
+static int tables_computed = 0;
+
+/**********************************************************************************************
+
+ compute_tables -- compute the difference tables
+
+***********************************************************************************************/
+
+static void compute_tables(void)
+{
+ /* nibble to bit map */
+ static const int nbl2bit[16][4] =
+ {
+ { 1, 0, 0, 0}, { 1, 0, 0, 1}, { 1, 0, 1, 0}, { 1, 0, 1, 1},
+ { 1, 1, 0, 0}, { 1, 1, 0, 1}, { 1, 1, 1, 0}, { 1, 1, 1, 1},
+ {-1, 0, 0, 0}, {-1, 0, 0, 1}, {-1, 0, 1, 0}, {-1, 0, 1, 1},
+ {-1, 1, 0, 0}, {-1, 1, 0, 1}, {-1, 1, 1, 0}, {-1, 1, 1, 1}
+ };
+
+ int step, nib;
+
+ /* loop over all possible steps */
+ for (step = 0; step <= 48; step++)
+ {
+ /* compute the step value */
+ int stepval = floor(16.0 * pow(11.0 / 10.0, (double)step));
+
+ /* loop over all nibbles and compute the difference */
+ for (nib = 0; nib < 16; nib++)
+ {
+ diff_lookup[step*16 + nib] = nbl2bit[nib][0] *
+ (stepval * nbl2bit[nib][1] +
+ stepval/2 * nbl2bit[nib][2] +
+ stepval/4 * nbl2bit[nib][3] +
+ stepval/8);
+ }
+ }
+
+ tables_computed = 1;
+}
+
+
+
+/**********************************************************************************************
+
+ reset_adpcm -- reset the ADPCM stream
+
+***********************************************************************************************/
+
+static void reset_adpcm(struct ADPCMVoice *voice)
+{
+ /* make sure we have our tables */
+ if (!tables_computed)
+ compute_tables();
+
+ /* reset the signal/step */
+ voice->signal = -2;
+ voice->step = 0;
+}
+
+
+const device_type OKIM6376 = &device_creator<okim6376_device>;
+
+okim6376_device::okim6376_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
+ : device_t(mconfig, OKIM6376, "OKI6376", tag, owner, clock, "okim6376", __FILE__),
+ device_sound_interface(mconfig, *this),
+ m_region_base(*this, DEVICE_SELF),
+ //m_command[OKIM6376_VOICES],
+ m_latch(0),
+ //m_stage[OKIM6376_VOICES],
+ m_stream(NULL),
+ m_master_clock(0),
+ m_divisor(0),
+ m_channel(0),
+ m_nar(0),
+ m_nartimer(0),
+ m_busy(0),
+ m_ch2(0),
+ m_st(0),
+ m_st_pulses(0),
+ m_ch2_update(0),
+ m_st_update(0)
+{
+}
+
+//-------------------------------------------------
+// device_config_complete - perform any
+// operations now that the configuration is
+// complete
+//-------------------------------------------------
+
+void okim6376_device::device_config_complete()
+{
+}
+
+//-------------------------------------------------
+// device_start - device-specific startup
+//-------------------------------------------------
+
+void okim6376_device::device_start()
+{
+ int voice;
+ compute_tables();
+
+ m_command[0] = -1;
+ m_command[1] = -1;
+ m_stage[0] = 0;
+ m_stage[1] = 0;
+ m_latch = 0;
+ m_master_clock = clock();
+ m_divisor = divisor_table[0];
+ m_nar = 1;
+ m_nartimer = 0;
+ m_busy = 1;
+ m_st = 1;
+ m_ch2 = 1;
+ m_st_update = 0;
+ m_ch2_update = 0;
+ m_st_pulses = 0;
+ /* generate the name and create the stream */
+ m_stream = machine().sound().stream_alloc(*this, 0, 1, clock() / m_divisor);
+
+ /* initialize the voices */
+ for (voice = 0; voice < OKIM6376_VOICES; voice++)
+ {
+ /* initialize the rest of the structure */
+ m_voice[voice].volume = 0;
+ reset_adpcm(&m_voice[voice]);
+ }
+
+ okim6376_state_save_register();
+}
+
+//-------------------------------------------------
+// device_reset - device-specific reset
+//-------------------------------------------------
+
+void okim6376_device::device_reset()
+{
+ int i;
+
+ m_stream->update();
+ for (i = 0; i < OKIM6376_VOICES; i++)
+ m_voice[i].playing = 0;
+}
+
+
+/**********************************************************************************************
+
+ clock_adpcm -- clock the next ADPCM byte
+
+***********************************************************************************************/
+
+static INT16 clock_adpcm(struct ADPCMVoice *voice, UINT8 nibble)
+{
+ voice->signal += diff_lookup[voice->step * 16 + (nibble & 15)];
+
+ /* clamp to the maximum 12bit */
+ if (voice->signal > 2047)
+ voice->signal = 2047;
+ else if (voice->signal < -2048)
+ voice->signal = -2048;
+
+ /* adjust the step size and clamp */
+ voice->step += index_shift[nibble & 7];
+ if (voice->step > 48)
+ voice->step = 48;
+ else if (voice->step < 0)
+ voice->step = 0;
+
+ /* return the signal */
+ return voice->signal;
+}
+
+
+void okim6376_device::oki_process(int channel, int command)
+{
+ /* if a command is pending, process the second half */
+ if ((command != -1) && (command != 0)) //process silence separately
+ {
+ int start;
+ unsigned char *base/*, *base_end*/;
+ /* update the stream */
+ m_stream->update();
+
+ /* determine which voice(s) (voice is set by the state of 2CH) */
+ {
+ struct ADPCMVoice *voice = &m_voice[channel];
+
+ /* determine the start position, max address space is 16Mbit */
+ base = &m_region_base[m_command[channel] * 4];
+ //base_end = &m_region_base[(MAX_WORDS+1) * 4];
+ start = ((base[0] << 16) + (base[1] << 8) + base[2]) & 0x1fffff;
+
+ if (start == 0)
+ {
+ voice->playing = 0;
+ }
+ else
+ {
+ /* set up the voice to play this sample */
+ if (!voice->playing)
+ {
+ voice->playing = 1;
+ voice->base_offset = start;
+ voice->sample = 0;
+ voice->count = 0;
+
+ /* also reset the ADPCM parameters */
+ reset_adpcm(voice);
+ if (channel == 0)
+ {
+ /* We set channel 2's audio separately */
+ voice->volume = volume_table[0];
+ }
+ }
+ else
+ {
+ if (((m_nar)&&(channel == 0))||(channel == 1))//Store the request, for later processing (channel 2 ignores NAR)
+ {
+ m_stage[channel] = 1;
+ }
+ }
+ }
+ }
+ }
+ /* otherwise, see if this is a silence command */
+ else
+ {
+ /* update the stream, then turn it off */
+ m_stream->update();
+
+ if (command ==0)
+ {
+ int i;
+ for (i = 0; i < OKIM6376_VOICES; i++)
+ {
+ struct ADPCMVoice *voice = &m_voice[i];
+ voice->playing = 0;
+ }
+ }
+ }
+}
+
+
+/**********************************************************************************************
+
+ generate_adpcm -- general ADPCM decoding routine
+
+***********************************************************************************************/
+
+void okim6376_device::generate_adpcm(struct ADPCMVoice *voice, INT16 *buffer, int samples,int channel)
+{
+ /* if this voice is active */
+ if (voice->playing)
+ {
+ UINT8 *base = m_region_base + voice->base_offset;
+ int sample = voice->sample;
+ int count = voice->count;
+
+ /* loop while we still have samples to generate */
+ while (samples)
+ {
+ int nibble;
+
+ if (count == 0)
+ {
+ /* get the number of samples to play */
+ count = (base[sample / 2] & 0x7f) << 1;
+
+ /* end of voice marker */
+ if (count == 0)
+ {
+ voice->playing = 0;
+ break;
+ }
+ else
+ {
+ /* step past the count byte */
+ sample += 2;
+ }
+ }
+
+ /* compute the new amplitude and update the current step */
+ nibble = base[sample / 2] >> (((sample & 1) << 2) ^ 4);
+
+ /* output to the buffer, scaling by the volume */
+ /* signal in range -4096..4095, volume in range 2..16 => signal * volume / 2 in range -32768..32767 */
+ *buffer++ = clock_adpcm(voice, nibble) * voice->volume / 2;
+
+ ++sample;
+ --count;
+ --samples;
+ }
+
+ /* update the parameters */
+ voice->sample = sample;
+ voice->count = count;
+ }
+
+ /* fill the rest with silence */
+ while (samples--)
+ *buffer++ = 0;
+
+ if ((!voice->playing)&&(m_stage[channel]))//end of samples, load anything staged in
+ {
+ m_stage[channel] = 0;
+ oki_process(channel,m_command[channel]);
+ }
+}
+
+
+/**********************************************************************************************
+
+ state save support for MAME
+
+***********************************************************************************************/
+
+void okim6376_device::postload()
+{
+ set_frequency(m_master_clock);
+}
+
+void okim6376_device::adpcm_state_save_register(struct ADPCMVoice *voice, int index)
+{
+ save_item(NAME(voice->playing), index);
+ save_item(NAME(voice->sample), index);
+ save_item(NAME(voice->count), index);
+ save_item(NAME(voice->signal), index);
+ save_item(NAME(voice->step), index);
+ save_item(NAME(voice->volume), index);
+ save_item(NAME(voice->base_offset), index);
+}
+
+void okim6376_device::okim6376_state_save_register()
+{
+ int j;
+ for (j = 0; j < OKIM6376_VOICES; j++)
+ {
+ adpcm_state_save_register(&m_voice[j], j);
+ }
+ machine().save().register_postload(save_prepost_delegate(FUNC(okim6376_device::postload), this));
+ save_item(NAME(m_command[0]));
+ save_item(NAME(m_command[1]));
+ save_item(NAME(m_stage[0]));
+ save_item(NAME(m_stage[1]));
+ save_item(NAME(m_latch));
+ save_item(NAME(m_divisor));
+ save_item(NAME(m_nar));
+ save_item(NAME(m_nartimer));
+ save_item(NAME(m_busy));
+ save_item(NAME(m_st));
+ save_item(NAME(m_st_pulses));
+ save_item(NAME(m_st_update));
+ save_item(NAME(m_ch2));
+ save_item(NAME(m_ch2_update));
+ save_item(NAME(m_master_clock));
+}
+
+void okim6376_device::set_frequency(int frequency)
+{
+ m_master_clock = frequency;
+ m_stream->set_sample_rate(m_master_clock / m_divisor);
+}
+
+
+/**********************************************************************************************
+
+ okim6376_status_r -- read the status port of an OKIM6376-compatible chip
+
+***********************************************************************************************/
+
+READ_LINE_MEMBER( okim6376_device::busy_r )
+{
+ struct ADPCMVoice *voice0 = &m_voice[0];
+ struct ADPCMVoice *voice1 = &m_voice[1];
+
+ /* set the bit low if it's playing */
+ if ((voice0->playing)||(voice1->playing))
+ {
+ return 0;
+ }
+ else
+ {
+ return 1;
+ }
+}
+
+READ_LINE_MEMBER( okim6376_device::nar_r )
+{
+ MSM6376LOG(("OKIM6376:'%s' NAR %x\n",tag(),m_nar));
+ return m_nar;
+}
+
+WRITE_LINE_MEMBER( okim6376_device::ch2_w )
+{
+ m_ch2_update = 0;//Clear flag
+ MSM6376LOG(("OKIM6376:'%s' CH2 %x\n",tag(),state));
+
+ if (m_ch2 != state)
+ {
+ m_ch2 = state;
+ m_ch2_update = 1;
+ }
+ if((!m_ch2)&&(m_ch2_update))
+ {
+ m_st_pulses = 0;
+ struct ADPCMVoice *voice0 = &m_voice[0];
+ struct ADPCMVoice *voice1 = &m_voice[1];
+ // We set to channel 2
+ MSM6376LOG(("OKIM6376:'%s' Channel 1\n",tag()));
+ m_channel = 1;
+
+ if ((voice0->playing)&&(m_st))
+ {
+ //Echo functions when Channel 1 is playing, and ST is still high
+ m_command[1] = m_command[0];//copy sample over
+ voice1->volume = volume_table[1]; //echo is 6dB attenuated
+ }
+ }
+
+ if((m_ch2)&&(m_ch2_update))
+ {
+ m_stage[1]=0;
+ oki_process(1, m_command[1]);
+ MSM6376LOG(("OKIM6376:'%s' Channel 0\n",tag()));
+ m_channel = 0;
+ }
+}
+
+
+WRITE_LINE_MEMBER( okim6376_device::st_w )
+{
+ //As in STart, presumably, this triggers everything
+
+ m_st_update = 0;//Clear flag
+ MSM6376LOG(("OKIM6376:'%s' ST %x\n",tag(),state));
+
+ if (m_st != state)
+ {
+ m_st = state;
+ m_st_update = 1;
+
+ if ((m_channel == 1) & !m_st)//ST acts as attenuation for Channel 2 when low, and stays at that level until the channel is reset
+ {
+ struct ADPCMVoice *voice = &m_voice[m_channel];
+ {
+ m_st_pulses ++;
+ MSM6376LOG(("OKIM6376:'%s' ST pulses %x\n",tag(),m_st_pulses));
+ if (m_st_pulses > 3)
+ {
+ m_st_pulses = 3; //undocumented behaviour beyond 3 pulses
+ }
+
+ voice->volume = volume_table[m_st_pulses - 1];
+ }
+ }
+ if (m_st && m_st_update)
+ {
+ m_command[m_channel] = m_latch;
+ if (m_channel ==0 && m_nar)
+ {
+ m_stage[m_channel]=0;
+ oki_process(0, m_command[0]);
+ m_nar = 0;
+ m_nartimer = 4;
+ /*According to datasheet, NAR timing is ~375 us at 8KHz, and is inversely proportional to sample rate, effectively 6 stream updates. */
+ }
+ }
+ }
+}
+
+/**********************************************************************************************
+
+ okim6376_data_w -- write to the data port of an OKIM6376-compatible chip
+
+***********************************************************************************************/
+
+WRITE8_MEMBER( okim6376_device::write )
+{
+ // The data port is purely used to set the latch, everything else is started by an ST pulse
+
+ m_latch = data & 0x7f;
+ // FIX: maximum adpcm words are 111, there are other 8 commands to generate BEEP tone (0x70 to 0x77),
+ // and others for internal testing, that manual explicitly says not to use (0x78 to 0x7f)
+ // We aren't doing anything with the BEEP at the moment, as we'd need to mix the ADPCM stream with beep.c
+}
+
+//-------------------------------------------------
+// sound_stream_update - handle a stream update
+//-------------------------------------------------
+
+void okim6376_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
+{
+ int i;
+
+ memset(outputs[0], 0, samples * sizeof(*outputs[0]));
+
+ for (i = 0; i < OKIM6376_VOICES; i++)
+ {
+ struct ADPCMVoice *voice = &m_voice[i];
+ stream_sample_t *buffer = outputs[0];
+ INT16 sample_data[MAX_SAMPLE_CHUNK];
+ int remaining = samples;
+ if (i == 0) //channel 1 is the only channel to affect NAR
+ {
+ if (m_nartimer > 0)
+ {
+ m_nartimer--;
+ if (!m_nartimer)
+ {
+ m_nar =1;
+ }
+ }
+ }
+
+ /* loop while we have samples remaining */
+ while (remaining)
+ {
+ int samples = (remaining > MAX_SAMPLE_CHUNK) ? MAX_SAMPLE_CHUNK : remaining;
+ int samp;
+
+ generate_adpcm(voice, sample_data, samples,i);
+ for (samp = 0; samp < samples; samp++)
+ *buffer++ += sample_data[samp];
+
+ remaining -= samples;
+ }
+ }
+}