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PSG noise latch only reset on change of noise type, not on any noise control write (not sure if this change is strictly correct).

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Tweaked noise frequency.
Fixes noise in Zak McKracken.
This commit is contained in:
TomW 2015-11-24 20:47:49 +00:00
commit f17c9dbb22
1 changed files with 5 additions and 6 deletions
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11
src/sound_sn76489.c
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@ -58,7 +58,7 @@ void sn76489_poll(void *p)
sn76489->count[0] -= (512 * PSGCONST);
while ((int)sn76489->count[0] < 0 && sn76489->latch[0])
{
sn76489->count[0] += (sn76489->latch[0] * 2);
sn76489->count[0] += (sn76489->latch[0] * 4);
if (!(sn76489->noise & 4))
{
if (sn76489->shift & 1)
@ -135,8 +135,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
sn76489->vol[1] = 0xf - data;
break;
case 0x60:
sn76489->shift = 0x4000;
if ((data & 3) != (sn76489->noise & 3)) sn76489->count[0] = 0;
if ((data & 4) != (sn76489->noise & 4))
sn76489->shift = 0x4000;
sn76489->noise = data & 0xf;
if ((data & 3) == 3) sn76489->latch[0] = sn76489->latch[1];
else sn76489->latch[0] = 0x400 << (data & 3);
@ -153,9 +153,8 @@ void sn76489_write(uint16_t addr, uint8_t data, void *p)
{
if ((sn76489->firstdat & 0x70) == 0x60)
{
sn76489->shift = 0x4000;
if ((data & 3) != (sn76489->noise & 3))
sn76489->count[0] = 0;
if ((data & 4) != (sn76489->noise & 4))
sn76489->shift = 0x4000;
sn76489->noise = data & 0xf;
if ((data & 3) == 3) sn76489->latch[0] = sn76489->latch[1];
else sn76489->latch[0] = 0x400 << (data & 3);