[avr-gcc-list] How to get the mega8's RXD pin level?

[whiteman]

hi,all！

I have a project about DMX512. I have put the PORTD0(RXD)&PORTD1(TXD) to the 
USART function. In my code, I want to check the

RXD pin LEVEL without change the RXD pin to NORMAL I/O function. I download my 
code and run, but the ATmega8 is hang.  Later,

I connet the another I/O pin(i.e. PORTC5) to RXD pin, and check the PORTC5. But 
I get the same result, the ATmega8 is hang. How can I do? thanks.
Here is my partion of code:


void USART_Init(uint16_t baud)
{
        cli();  
        UBRRH = baud >> 8;
        UBRRL = baud;   //
        UCSRA  = 1 << U2X;      //
        UCSRB = (1 << RXCIE)|(1 << TXCIE)|(1 << RXEN)|(1 << TXEN);//
        UCSRC = (1 << URSEL)|(1 << USBS)|(0 << UCSZ0);//
        sei();  
}

int main(void)
{
        PORTD |= 0x01;  //Enable the RXD pull-up resistor
        USART_Init(4);
        while(1)
        {
                if(P_RXD)
                {
                        Task1();
                }
                else
                {
                        Task2();
                }

        }
}

best regard!                            

　　　　　　　　whiteman
address@hidden
　　　　　　　　　　2004-06-25