playNote.c

#include <stdlib.h>
#include <x86.h>

#define lastIntroNote 0+26*2
#define lastNote song_LEN // very last entry in song

unsigned int soundIndex = 0; // NTS: use song only for indexing. NOTE: may want to expand
unsigned short soundWait = 0;

// NOTE: this is supposed to run per tick
void playNote(){
	if (soundIndex > lastNote)
		soundIndex = lastIntroNote; // jump to loop point

	soundWait--;
	if (soundWait != -1) // quirk: not >
		return;

	unsigned short _cursor = song[soundIndex++]; // ax
	// ???: cx <- ah
	unsigned char *freq = (freq >> 8) & 0xff; // ah
	freq = freq & 0x1F; // and ah, 00011111b

	// Set the frequency
	IO_write(0x42, freq);

	soundWait = soundWait >> 5; // SHR
}