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YMZ280B: frequency precision improvement 

frequency is now multiplied by 256 and then fed to the chip divided by
256 to increase freq precision
This commit is contained in:
tildearrow 2022-07-22 00:01:29 -05:00
parent 5127d5ef18
commit 7bc3166ed5
1 changed files with 5 additions and 4 deletions
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9
src/engine/platform/ymz280b.cpp
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@ -23,7 +23,7 @@
#include <math.h>
#include <map>
#define CHIP_FREQBASE 98304
#define CHIP_FREQBASE 25165824
#define rWrite(a,v) {if(!skipRegisterWrites) {ymz280b.write(0,a); ymz280b.write(1,v); regPool[a]=v; if(dumpWrites) addWrite(a,v); }}
@ -142,7 +142,7 @@ void DivPlatformYMZ280B::tick(bool sysTick) {
default: ctrl=0;
}
double off=(s->centerRate>=1)?((double)s->centerRate/8363.0):1.0;
chan[i].freq=(int)(off*parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE))-1;
chan[i].freq=(int)round(off*parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE)/256.0)-1;
if (chan[i].freq<0) chan[i].freq=0;
if (chan[i].freq>511) chan[i].freq=511;
// ADPCM has half the range
@ -267,14 +267,15 @@ int DivPlatformYMZ280B::dispatch(DivCommand c) {
case DIV_CMD_NOTE_PORTA: {
int destFreq=NOTE_FREQUENCY(c.value2);
bool return2=false;
int multiplier=(parent->song.linearPitch==2)?1:256;
if (destFreq>chan[c.chan].baseFreq) {
chan[c.chan].baseFreq+=c.value;
chan[c.chan].baseFreq+=c.value*multiplier;
if (chan[c.chan].baseFreq>=destFreq) {
chan[c.chan].baseFreq=destFreq;
return2=true;
}
} else {
chan[c.chan].baseFreq-=c.value;
chan[c.chan].baseFreq-=c.value*multiplier;
if (chan[c.chan].baseFreq<=destFreq) {
chan[c.chan].baseFreq=destFreq;
return2=true;