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PSG period 0 now handled as 1024 - fixes bassline in Zak McKracken.

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This commit is contained in:
TomW 2015-11-24 20:46:37 +00:00
commit 1129e1c630
1 changed files with 14 additions and 2 deletions
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16
src/sound_sn76489.c
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@ -47,7 +47,7 @@ void sn76489_poll(void *p)
else result += (int16_t) (volslog[sn76489->vol[c]] * 127);
sn76489->count[c] -= (256 * PSGCONST);
while ((int)sn76489->count[c] < 0 && sn76489->latch[c])
while ((int)sn76489->count[c] < 0)
{
sn76489->count[c] += sn76489->latch[c];
sn76489->stat[c] = -sn76489->stat[c];
@ -104,6 +104,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
case 0:
sn76489->freqlo[3] = data & 0xf;
sn76489->latch[3] = (sn76489->freqlo[3] | (sn76489->freqhi[3] << 4)) << 6;
if (!sn76489->latch[3])
sn76489->latch[3] = 1024 << 6;
sn76489->lasttone = 3;
break;
case 0x10:
@ -113,6 +115,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
case 0x20:
sn76489->freqlo[2] = data & 0xf;
sn76489->latch[2] = (sn76489->freqlo[2] | (sn76489->freqhi[2] << 4)) << 6;
if (!sn76489->latch[2])
sn76489->latch[2] = 1024 << 6;
sn76489->lasttone = 2;
break;
case 0x30:
@ -122,6 +126,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
case 0x40:
sn76489->freqlo[1] = data & 0xf;
sn76489->latch[1] = (sn76489->freqlo[1] | (sn76489->freqhi[1] << 4)) << 6;
if (!sn76489->latch[1])
sn76489->latch[1] = 1024 << 6;
sn76489->lasttone = 1;
break;
case 0x50:
@ -134,6 +140,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
sn76489->noise = data & 0xf;
if ((data & 3) == 3) sn76489->latch[0] = sn76489->latch[1];
else sn76489->latch[0] = 0x400 << (data & 3);
if (!sn76489->latch[0])
sn76489->latch[0] = 1024 << 6;
break;
case 0x70:
data &= 0xf;
@ -151,13 +159,17 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
sn76489->noise = data & 0xf;
if ((data & 3) == 3) sn76489->latch[0] = sn76489->latch[1];
else sn76489->latch[0] = 0x400 << (data & 3);
if (!sn76489->latch[0])
sn76489->latch[0] = 1024 << 6;
}
else
{
sn76489->freqhi[sn76489->lasttone] = data & 0x3F;
freq = sn76489->freqlo[sn76489->lasttone] | (sn76489->freqhi[sn76489->lasttone] << 4);
if (!freq)
freq = 1024;
if ((sn76489->noise & 3) == 3 && sn76489->lasttone == 1)
sn76489->latch[0] = freq << 6;
sn76489->latch[0] = freq << 6;
sn76489->latch[sn76489->lasttone] = freq << 6;
}
}