I am working on a project which need to use the DTMF chip and AT89c51.
and I have read the datasheet for many times and no problem to send DTMF signal out.
However, i got some difficulty to read the input tone.
i am during with this bug for nearly 2 weeks.
I guess i may have something want about reading the status resgister.
and I can clear the interrupt flag even read the staus register.

please kindly give some idea to me.
or any suggestion about using the MT8888.

char Read_Creg(){
char tempCreg;

P1=0xff;
RS_0=1;
delay(20);
READ=0;
tempCreg=P1;
READ=1;
tempCreg=(tempCreg & 0x0f);
return tempCreg;
}


char Read_Rreg()
{
char tempRreg;
P1=0xff;
RS_0=0;
delay(20);
READ=0;
tempRreg=P1;
READ=1;
tempRreg=(tempRreg & 0x0f);
return tempRreg;
}



void getdtmf() interrupt 0 using 1
{

unsigned char tempCreg1;
unsigned char tempCreg2;
unsigned char ReceiveData;

tempCreg1=Read_Creg;
delay(10);
P0=tempCreg1;
tempCreg2=tempCreg1;

tempCreg1=(tempCreg1 & 0x04); //check ready for next tone
tempCreg2=(tempCreg2 & 0x02); //chech for received tone

if (tempCreg1==0x04)
{ToneSendReady=1;} //flag for check tone ready to send

if (tempCreg2 ==0x02)
{ ReceiveData=Read_Rreg();
P0=ReceiveData;
}
}