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snkwave.cpp: Fix frequency register bit alignment as well as waveform sample bit alignment based on the schematics and observations of running games. Fixes wrong laser/other sounds in Vanguard II and some wrong sounds in Marvin's Maze. [Lord Nightmare]

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Lord-Nightmare 2024-11-13 15:42:28 -05:00
parent ca721f71f2
commit a32e9f3a48
1 changed files with 6 additions and 9 deletions
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15
src/devices/sound/snkwave.cpp
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@ -119,14 +119,11 @@ void snkwave_device::snkwave_w(offs_t offset, uint8_t data)
{
m_stream->update();
// all registers are 6-bit
data &= 0x3f;
if (offset == 0)
m_frequency = (m_frequency & 0x03f) | (data << 6);
else if (offset == 1)
m_frequency = (m_frequency & 0xfc0) | data;
else if (offset <= 5)
if (offset == 0) // F1, high 6 bits
m_frequency = (m_frequency & 0x03f) | ((data & 0xfc) << 4);
else if (offset == 1) // F2, low 6 bits
m_frequency = (m_frequency & 0xfc0) | (data & 0x3f);
else if (offset <= 5) // W3 thru W6, low 3 bits of each nybble
update_waveform(offset - 2, data);
}
@ -143,7 +140,7 @@ void snkwave_device::update_waveform(unsigned int offset, uint8_t data)
{
assert(offset < WAVEFORM_LENGTH/4);
m_waveform[offset * 2] = ((data & 0x38) >> 3) << (12-CLOCK_SHIFT);
m_waveform[offset * 2] = ((data & 0x70) >> 4) << (12-CLOCK_SHIFT);
m_waveform[offset * 2 + 1] = ((data & 0x07) >> 0) << (12-CLOCK_SHIFT);
m_waveform[WAVEFORM_LENGTH-2 - offset * 2] = ~m_waveform[offset * 2 + 1];
m_waveform[WAVEFORM_LENGTH-1 - offset * 2] = ~m_waveform[offset * 2];