iar

void uart_putchar (UART_MemMapPtr channel, char ch)
{
/* Wait until space is available in the FIFO */
while(!(UART_S1_REG(channel) & UART_S1_TDRE_MASK));
/* Send the character */
UART_D_REG(channel) = (uint8)ch;
}
陷入这个死循环 怎么解！！