Hi Mario,

Your mistake is that you have mixed up the status register bits. Bit 2 (0x02) means TxRegisterEmpty, but you use it to get received data. Bit 3 (0x04) means ValidRxData, but you use it to set the ReadyToSend flag.

You have to just change this bits.

And one more thing. That's definitely not my busyness but your program is a little bit messy so I brushed it up.

char ReadReg()
{
char tempReg;
delay(20);
READ=0;
tempReg=P1;
READ=1;
return tempReg;
}

void getdtmf() interrupt 0 using 1
{
unsigned char tempCreg;
P1=0xff;
RS0=1;
tempCreg=ReadReg();
delay(10);
if(tempCreg&&0x02)ToneSendReady=1;
RS0=0;
if(tempCreg&&0x04)P0=ReadReg();
}

Best regards,
George