Circular buffer for STA013

[micman]

Hi all,
I have a problem with circular buffer.
I work with a pic18f8720 at 20MHz, an interface atapi and sta013 decoder a MPEG.

I only have a buffer of 2048 byte "int8 mp3data[2048 ]" and I can read byte for byte for "mp3data" and send to STA013 when data request is set.
The problem is: Where reload data to buffer "mp3data".
I've a function "ata_read_sector(0,g,mp3data);" return 512byte data to mp3data
The code example is inclomplete becose i don't write code for circular buffer!
The music load is only 64Kbps!!!
Thank for help me!!

int32 g;
int8 mp3data[2048];
int16 mp3ptr,bufptr;


g = 48119; //Sector where there is gives data mp3
mp3ptr=0; //pointer read
bufptr=0; //pointer write
ata_read_sector(0,g,mp3data); //read sector 512 byte
g++; //incremento sector
ata_read_sector(0,g,&mp3data[512]); //read sector 512 byte
g++;
ata_read_sector(0,g,&mp3data[1024]); //read sector 512 byte
g++;
ata_read_sector(0,g,&mp3data[1536]); //read sector 512 byte

for(;;){
while(input(DATA_REQ)){ //STA013 request data!!!
for(it=7;it<255;it--){
output_low(SCKR);
dato = mp3data[mp3ptr];
output_bit(SDI,((errore>>it)&1));
output_high(SCKR);
}
mp3ptr++;
if(mp3ptr>=2048) mp3ptr=0;
//????????????????? Circular buffer??//how to????
// g++
//ata_read_sector(0,g,&mp3data[]) //function reload 512 chunk
}//while

}//for

[PCM programmer]

For sample code on circular buffers, look at the EX_SISR.C
example file, in this folder: c:\Program Files\Picc\Examples
You will have to modify the code somewhat, because that
example is for a small buffer (less than 256 bytes), and
you have a large buffer. ie., the index values must be
16-bit for your program, instead of 8-bit as in the example.