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-rw-r--r--src/mame/audio/socrates.c127
1 files changed, 127 insertions, 0 deletions
diff --git a/src/mame/audio/socrates.c b/src/mame/audio/socrates.c
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+// license:BSD-3-Clause
+// copyright-holders:Jonathan Gevaryahu
+/***************************************************************************
+
+ audio/socrates.c
+ Copyright (C) 2010-2011 Jonathan Gevaryahu AKA Lord Nightmare
+
+ This handles the two squarewaves (plus the one weird wave) channels
+ on the V-tech Socrates system 27-0769 ASIC.
+
+
+****************************************************************************/
+
+#include "emu.h"
+#include "socrates.h"
+
+
+// device type definition
+const device_type SOCRATES_SOUND = &device_creator<socrates_snd_device>;
+
+
+//-------------------------------------------------
+// socrates_snd_device - constructor
+//-------------------------------------------------
+
+socrates_snd_device::socrates_snd_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
+ : device_t(mconfig, SOCRATES_SOUND, "Socrates Sound", tag, owner, clock, "socrates_snd", __FILE__),
+ device_sound_interface(mconfig, *this)
+{
+}
+
+
+//-------------------------------------------------
+// device_start - device-specific startup
+//-------------------------------------------------
+
+void socrates_snd_device::device_start()
+{
+ m_freq[0] = m_freq[1] = 0xff; /* channel 1,2 frequency */
+ m_vol[0] = m_vol[1] = 0x07; /* channel 1,2 volume */
+ m_enable[0] = m_enable[1] = 0x01; /* channel 1,2 enable */
+ m_channel3 = 0x00; /* channel 3 weird register */
+ m_DAC_output = 0x00; /* output */
+ m_state[0] = m_state[1] = m_state[2] = 0;
+ m_accum[0] = m_accum[1] = m_accum[2] = 0xFF;
+ m_stream = machine().sound().stream_alloc(*this, 0, 1, clock() ? clock() : machine().sample_rate());
+}
+
+
+//-------------------------------------------------
+// sound_stream_update - handle a stream update
+//-------------------------------------------------
+
+void socrates_snd_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
+{
+ for (int i = 0; i < samples; i++)
+ {
+ snd_clock();
+ outputs[0][i] = ((int)m_DAC_output<<4);
+ }
+}
+
+
+const UINT8 socrates_snd_device::s_volumeLUT[16] =
+{
+0, 61, 100, 132, 158, 183, 201, 218,
+233, 242, 253, 255, 250, 240, 224, 211
+}; // this table is actually quite weird on the real console.
+// 0, 0.033, 0.055, 0.07175, 0.086, 0.1, 0.11, 0.119, 0.127, 0.132, 0.138, 0.139, 0.136, 0.131, 0.122, 0.115 are the voltage amplitudes for the steps on channel 2. the last four are particularly bizarre, probably caused by some sort of internal clipping.
+
+void socrates_snd_device::snd_clock() /* called once per clock */
+{
+ for (int channel = 0; channel < 2; channel++)
+ {
+ if ((m_accum[channel] == 0) && m_enable[channel])
+ {
+ m_state[channel] = (m_state[channel]^0x1);
+ m_accum[channel] = m_freq[channel];
+ }
+ else if (m_enable[channel])
+ {
+ m_accum[channel]--;
+ }
+ else
+ {
+ m_accum[channel] = 0; // channel is disabled
+ m_state[channel] = 0;
+ }
+ }
+ // handle channel 3 here
+ m_DAC_output = (m_state[0]?(s_volumeLUT[m_vol[0]]*9.4):0); // channel 1 is ~2.4 times as loud as channel 2
+ m_DAC_output += (m_state[1]?(s_volumeLUT[m_vol[1]]<<2):0);
+ // add channel 3 to dac output here
+}
+
+
+void socrates_snd_device::reg0_w(int data)
+{
+ m_stream->update();
+ m_freq[0] = data;
+}
+
+void socrates_snd_device::reg1_w(int data)
+{
+ m_stream->update();
+ m_freq[1] = data;
+}
+
+void socrates_snd_device::reg2_w(int data)
+{
+ m_stream->update();
+ m_vol[0] = data&0xF;
+ m_enable[0] = (data&0x10)>>4;
+}
+
+void socrates_snd_device::reg3_w(int data)
+{
+ m_stream->update();
+ m_vol[1] = data&0xF;
+ m_enable[1] = (data&0x10)>>4;
+}
+
+void socrates_snd_device::reg4_w(int data)
+{
+ m_stream->update();
+ m_channel3 = data;
+}