Hi, all
I want to send long string to SAM7S64 USART port. But some characters are missing
My code:

void InitUSART0(void)
{

u_pPio->PIO_PDR = BIT5 | BIT6 ; //Disables the PIO from controlling the corresponding pin (enables peripheral control of the pin).
u_pPio->PIO_ASR = BIT5 | BIT6 ; //Assigns the I/O line to the Peripheral A function.
u_pPio->PIO_BSR = 0; //Assigns the I/O line to the Peripheral B function.


//enable the clock of USART
u_pPMC->PMC_PCER = 1<<AT91C_ID_US0;

//set baud rate divisor register
u_pUSART0->US_BRGR = 313; //((48000000)/9600x16)

//write the Timeguard Register
u_pUSART0->US_TTGR = 0;

//Set the USART mode
u_pUSART0->US_MR = 0x08c0; // 8-bit mode, no parity, normal mode

//Enable the RX and TX PDC transfer requests
u_pPDC0->PDC_PTCR = AT91C_PDC_TXTEN | AT91C_PDC_RXTEN;

//Enable usart
u_pUSART0->US_CR = 0x50;

}

void write_char_USART0(unsigned char ch)
{
while (!(u_pUSART0->US_CSR&AT91C_US_TXRDY)==1);
u_pUSART0->US_THR = ((ch & 0x1FF));
}

void write_str_USART0(unsigned char* buff) {

unsigned int i = 0x0;

while(buff[i] != '\0') {
write_char_USART0(buff[i]);
i++;
}

}

Maybe this is a problem of main clock or PLL configuration ?

Thanks.

Or at the receiving end perhaps? What are you using as a terminal application? I'd generally recommend RealTerm, capturing in "Direct" mode (ie to a file, not the screen+file).

9600 baud is relatively slow, and oscillator/PLL timings tend to be far more stable/accurate than baud generators from decades past.

Have you examined the bit spacing on an oscilloscope? How about data sent from the receiver end.

Closely packed data can be a challenge for some receivers, sometimes using 2 stop-bits can help with inter-symbol separation.

If you are sending ASCII 8-bit data (unsigned char), why mask with 0x1FF? You'd be better casting and masking with 0xFF.