#define UART_RX_BUFFER_SIZE 16 /* 1,2,4,8,16,32,64,128 or 256 bytes */
#define UART_RX_BUFFER_MASK ( UART_RX_BUFFER_SIZE - 1 )
#define UART_TX_BUFFER_SIZE 16 /* 1,2,4,8,16,32,64,128 or 256 bytes */
#define UART_TX_BUFFER_MASK ( UART_TX_BUFFER_SIZE - 1 )
/* Static Variables */
static data unsigned char UART_RxBuf[UART_RX_BUFFER_SIZE];
static data volatile unsigned char UART_RxHead;
static data volatile unsigned char UART_RxTail;
static data unsigned char UART_TxBuf[UART_TX_BUFFER_SIZE];
static data volatile unsigned char UART_TxHead;
static data volatile unsigned char UART_TxTail;
bit fSeri0_Send_Ok;
/* initialize UART */
//t2 做波特率发生器 9600bps at 11.0592 MHz
void InitUART(   )
{
unsigned char x;
T2CON = 0x30;     //t2 做波特率发生器 
TH2 = 0xFF;
     TL2 = 0xdc;        
     RCAP2H = 0xFF;      
     RCAP2L = 0xdc;
     SCON = 0x50;         /* SM0 SM1 SM2 REN TB8 RB8 TI RI:9 bit */
     PCON = 0x00;         /* baut rate, 80h:double; 00h: normal   */
     ES = 1;              /* 串口中断允许    1-enable              */
     PS = 0;              /* 串口中断优先级 1-高，0-低            */
     TR2 = 1;             /* Start T2 as baut rate generator      */   
x = 0; /* flush receive buffer */
UART_RxTail = x;
UART_RxHead = x;
UART_TxTail = x;
UART_TxHead = x;
}
/* interrupt handlers */
void UART_interrupt( void ) interrupt 4
{
if (TI)
{ // 是否是发送中断
unsigned char tmptail;
TI=0;
   if (UART_TxTail==UART_TxHead)
   {
   fSeri0_Send_Ok=0;         /*已发送完毕*/ 
   }
   else
   {
   tmptail = ( UART_TxTail + 1 ) & UART_TX_BUFFER_MASK;
   UART_TxTail = tmptail; /* store new index */
   SBUF = UART_TxBuf[tmptail]; /* start
   transmition */
   }
}
if (RI)
{
unsigned char revdata;
unsigned char tmphead;
RI=0;
revdata = SBUF; 
tmphead = ( UART_RxHead + 1 ) & UART_RX_BUFFER_MASK;
UART_RxHead = tmphead; /* store new index */
UART_RxBuf[tmphead] = revdata; /* store received data in
buffer */
}
}

unsigned char ReceiveByte( void )
{
unsigned char tmptail;
while ( UART_RxHead == UART_RxTail );/* wait for incomming data */
tmptail = ( UART_RxTail + 1 ) & UART_RX_BUFFER_MASK;/* calculate buffer index */
UART_RxTail = tmptail; /* store new index */
return UART_RxBuf[tmptail]; /* return data */
}

void TransmitByte( unsigned char senddata )
{
unsigned char tmphead;
tmphead = ( UART_TxHead + 1 ) & UART_TX_BUFFER_MASK;
UART_TxBuf[tmphead] = senddata; /* store data in buffer */
UART_TxHead = tmphead; /* store new index */
if(fSeri0_Send_Ok==0)
   {
   fSeri0_Send_Ok=1;
   TI=1;
   }
}