大家帮忙看一下这个例程

发表于 2009-10-22 11:25

void main(void)
{
unsigned int i;
unsigned char counter;
/*High speed internal clock prescaler: 1*/
CLK_CKDIVR = 0x00;
UART2_CR2 = 0x00; //disable Tx & Rx
/* UART2 configured as follow:
      - BaudRate = 115200 baud
      - Word Length = 8 Bits
      - One Stop Bit
      - No parity
      - Receive and transmit enabled
      - UART2 Clock disabled
*/
/* Configure UART1 */
UART2_CR1  = 0x00;
UART2_CR3  = 0x00;
UART2_BRR2 = 0x0B;
UART2_BRR1 = 0x08;
UART2_CR2  = 0x0C;
counter = 0;
while(1)
{
   /* Output a message on Hyperterminal using printf function */
   printf("\nUART2 Example :Please press 1 key from keyboard. \n");
   for (i=0;i<10000;i++);
   /* Loop until the UART2 Receive Data Register is not empty */
   while (!(UART2_SR & 0x20));
   /* Store the received byte in RxBuffer */
   RxBuffer  = UART2_DR;
   printf("Key Pressed = %c.\n",RxBuffer);
}
}

/* -------------------------------------------------------------------------- */
/* ROUTINE NAME: putchar                                                    */
/* INPUT/OUTPUT: c Character to send.                                        */
/* DESCRIPTION:  Send character via UART to PC.                            */
/* -------------------------------------------------------------------------- */
char putchar (char c)
{
if (c == '\n')
{
   /* put '\r' to hardware here */
   /* Wait transmission is completed : otherwise the first data is not sent */
   while (!(UART2_SR & 0x40));
   UART2_DR = ('\r');
   /* Wait transmission is completed */
   while (!(UART2_SR & 0x40));
}
/* put c to hardware here */
/* Wait transmission is completed : otherwise the first data is not sent */
while (!(UART2_SR & 0x80));
UART2_DR = (c);
/* Wait transmission is completed */
while (!(UART2_SR & 0x80));
return (c);
}

这是个UART发送数据的例子，能发出数据，但是后面一个putchar函数看不懂什么意思，各位大侠帮忙解决一下。