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Diffstat (limited to 'src/mame/audio/socrates.c')
-rw-r--r-- | src/mame/audio/socrates.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/src/mame/audio/socrates.c b/src/mame/audio/socrates.c new file mode 100644 index 00000000000..c35896e5c25 --- /dev/null +++ b/src/mame/audio/socrates.c @@ -0,0 +1,127 @@ +// 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; +} |