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https://github.com/holub/mame
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iremga20: assume keyon is at reg 6 bit 1(not just any non-0 value), removed 2nd end of sample check, misc refactor and added notes (nw)
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@ -3,8 +3,17 @@
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/*********************************************************
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Irem GA20 PCM Sound Chip
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80 pin QFP, label NANAO GA20 (Nanao Corporation was Irem's parent company)
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It's not currently known whether this chip is stereo.
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TODO:
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- It's not currently known whether this chip is stereo.
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- Is sample position base(regs 0,1) used while sample is playing, or
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latched at key on? We've always emulated it the latter way.
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gunforc2 seems to be the only game updating the address regs sometimes
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while a sample is playing, but it doesn't seem intentional.
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- What is the 2nd sample address for? Is it end(cut-off) address, or
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loop start address? Every game writes a value that's past sample end.
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- All games write either 0 or 2 to reg #6, do other bits have any function?
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Revisions:
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@ -26,7 +35,7 @@ Revisions:
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02-03-2007 R. Belmont
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- Cleaned up faux x86 assembly.
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09-25-2018 Valley Bell
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09-25-2018 Valley Bell & co
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- rewrote channel update to make data 0 act as sample terminator
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*********************************************************/
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@ -36,8 +45,6 @@ Revisions:
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#include <algorithm>
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#define MAX_VOL 256
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// device type definition
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DEFINE_DEVICE_TYPE(IREMGA20, iremga20_device, "iremga20", "Irem GA20")
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@ -66,26 +73,16 @@ iremga20_device::iremga20_device(const machine_config &mconfig, const char *tag,
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void iremga20_device::device_start()
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{
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int i;
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iremga20_reset();
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std::fill(std::begin(m_regs), std::end(m_regs), 0);
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m_stream = stream_alloc(0, 2, clock()/4);
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save_item(NAME(m_regs));
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for (i = 0; i < 4; i++)
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for (int i = 0; i < 4; i++)
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{
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save_item(NAME(m_channel[i].rate), i);
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save_item(NAME(m_channel[i].size), i);
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save_item(NAME(m_channel[i].start), i);
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save_item(NAME(m_channel[i].pos), i);
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save_item(NAME(m_channel[i].frac), i);
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save_item(NAME(m_channel[i].end), i);
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save_item(NAME(m_channel[i].volume), i);
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save_item(NAME(m_channel[i].pan), i);
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save_item(NAME(m_channel[i].effect), i);
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save_item(NAME(m_channel[i].play), i);
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}
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}
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@ -97,7 +94,16 @@ void iremga20_device::device_start()
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void iremga20_device::device_reset()
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{
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iremga20_reset();
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std::fill(std::begin(m_regs), std::end(m_regs), 0);
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for (int i = 0; i < 4; i++)
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{
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m_channel[i].rate = 0;
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m_channel[i].pos = 0;
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m_channel[i].frac = 0;
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m_channel[i].end = 0;
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m_channel[i].volume = 0;
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m_channel[i].play = 0;
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}
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}
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//-------------------------------------------------
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@ -142,12 +148,12 @@ void iremga20_device::sound_stream_update(sound_stream &stream, stream_sample_t
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if (sample == 0x00) // check for sample end marker
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ch.play = 0;
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else
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{
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sampleout += (sample - 0x80) * (int32_t)ch.volume;
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ch.frac += ch.rate;
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ch.pos += (ch.frac >> 24);
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ch.frac &= ((1 << 24) - 1);
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if (ch.pos >= ch.end) // for safety (the actual chip probably doesn't check this)
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ch.play = 0;
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ch.frac += ch.rate;
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ch.pos += (ch.frac >> 24);
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ch.frac &= ((1 << 24) - 1);
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}
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}
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}
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@ -159,86 +165,64 @@ void iremga20_device::sound_stream_update(sound_stream &stream, stream_sample_t
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WRITE8_MEMBER( iremga20_device::irem_ga20_w )
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{
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int channel;
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//logerror("GA20: Offset %02x, data %04x\n",offset,data);
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m_stream->update();
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channel = offset >> 3;
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offset &= 0x1f;
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m_regs[offset] = data;
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int ch = offset >> 3;
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// channel regs:
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// 0,1: start address
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// 2,3: end? address
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// 4: rate
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// 5: volume
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// 6: control
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// 7: voice status (read-only)
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switch (offset & 0x7)
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{
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case 0: /* start address low */
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m_channel[channel].start = ((m_channel[channel].start)&0xff000) | (data<<4);
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break;
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case 1: /* start address high */
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m_channel[channel].start = ((m_channel[channel].start)&0x00ff0) | (data<<12);
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break;
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case 2: /* end? address low */
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m_channel[channel].end = ((m_channel[channel].end)&0xff000) | (data<<4);
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break;
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case 3: /* end? address high */
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m_channel[channel].end = ((m_channel[channel].end)&0x00ff0) | (data<<12);
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break;
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case 4:
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m_channel[channel].rate = (1 << 24) / (256 - data);
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m_channel[ch].rate = (1 << 24) / (256 - data);
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break;
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case 5: //AT: gain control
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m_channel[channel].volume = (data * MAX_VOL) / (data + 10);
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case 5:
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m_channel[ch].volume = (data * 256) / (data + 10);
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break;
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case 6: //AT: this is always written 2(enabling both channels?)
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m_channel[channel].play = data;
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m_channel[channel].pos = m_channel[channel].start;
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m_channel[channel].frac = 0;
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case 6:
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// d1: key on/off
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if (data & 2)
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{
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m_channel[ch].play = 1;
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m_channel[ch].pos = (m_regs[ch << 3 | 0] | m_regs[ch << 3 | 1] << 8) << 4;
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m_channel[ch].end = (m_regs[ch << 3 | 2] | m_regs[ch << 3 | 3] << 8) << 4;
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m_channel[ch].frac = 0;
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}
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else
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m_channel[ch].play = 0;
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// other: unknown/unused
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// possibilities are: loop flag, left/right speaker(stereo)
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break;
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}
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}
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READ8_MEMBER( iremga20_device::irem_ga20_r )
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{
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int channel;
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m_stream->update();
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channel = offset >> 3;
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offset &= 0x1f;
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int ch = offset >> 3;
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switch (offset & 0x7)
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{
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case 7: // voice status. bit 0 is 1 if active. (routine around 0xccc in rtypeleo)
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return m_channel[channel].play ? 1 : 0;
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case 7: // voice status. bit 0 is 1 if active. (routine around 0xccc in rtypeleo)
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return m_channel[ch].play;
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default:
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logerror("GA20: read unk. register %d, channel %d\n", offset & 0xf, channel);
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logerror("GA20: read unk. register %d, channel %d\n", offset & 0x7, ch);
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break;
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}
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return 0;
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}
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void iremga20_device::iremga20_reset()
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{
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int i;
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for( i = 0; i < 4; i++ ) {
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m_channel[i].rate = 0;
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m_channel[i].size = 0;
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m_channel[i].start = 0;
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m_channel[i].pos = 0;
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m_channel[i].frac = 0;
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m_channel[i].end = 0;
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m_channel[i].volume = 0;
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m_channel[i].pan = 0;
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m_channel[i].effect = 0;
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m_channel[i].play = 0;
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}
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}
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@ -44,21 +44,15 @@ private:
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struct channel_def
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{
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uint32_t rate;
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uint32_t size;
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uint32_t start;
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uint32_t pos;
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uint32_t frac;
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uint32_t end;
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uint32_t volume;
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uint32_t pan;
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uint32_t effect;
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uint32_t play;
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};
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void iremga20_reset();
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sound_stream *m_stream;
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uint8_t m_regs[0x40/2];
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uint8_t m_regs[0x20];
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channel_def m_channel[4];
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};
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