following is a code sequence used to initilze mt 8880 according to its datasheet. we have used this code successfully in our projects. it is for fixed duration. but may help u to test your Circuit it may also have problem. How you are testing generated tone . we used to connecte MT output to speacker to hear our tones.Thanks


void InitMT()
{
ReadStatus();
WriteControl(0x00);
WriteControl(0x00);
WriteControl(0x80);
WriteControl(0x00);
ReadStatus();
delay(); //adjust it accoridnt to your crystal setting and MT data sheet
WriteControl(0x80); //1000
WriteControl(0x00); //0000

}//InitMt


void WriteControl(unsigned char command)
{ //higher nibble contains four bit data, it is connected to data pins of 8880.
P3=command;
delay();
P1=0x0A; //1010;
delay();
CLK=0;
CS=1;
}//writeControl