串口第一位不输出

sunsungang

  在没有操作的情况下，输出应为ffddab，但实际输出fddab

#include "led.h"
#include "delay.h"
#include "sys.h"
#include "usart.h"
//ALIENTEK Mini STM32??·?°?·????ú??3
//?®?????é   
//?????§????www.openedv.com
//?????????í??×?????????????
 int main(void)
 {
u8 t;
u8 len;
u16 times=0; 
char a[6]={'f','f','d','d','a','b'};
 
delay_init();     //???±??????????
NVIC_Configuration();// ?è????????????·?×é
uart_init(9600); //?®??????????9600
LED_Init();   //????????LED?????????????? 
 
while(1)
{
if(USART_RX_STA&0x8000)
{
      LED0=!LED0;
len=USART_RX_STA&0x3fff;//?????????????????????¤??
printf("\r\n?ú·???????????:\r\n");
for(t=0;t<len;t++)
{
USART1->DR=USART_RX_BUF[t];
while((USART1->SR&0X40)==0);//????·????á??
}
printf("\r\n\r\n");//????????
USART_RX_STA=0;
}else
{
times++;
if(times%200==0)
{
   for(t=1;t<7;t++)
{
USART1->DR=a[t-1];
while((USART1->SR&0X40)==0);//????·????á??
}
printf("\r\n\r\n");//????????
}
delay_ms(10);   
}
}  
}

输出结果只有#include "led.h"
#include "delay.h"
#include "sys.h"
#include "usart.h"
//ALIENTEK Mini STM32??·?°?·????ú??3
//?®?????é   
//?????§????www.openedv.com
//?????????í??×?????????????
 int main(void)
 {
u8 t;
u8 len;
u16 times=0; 
char a[6]={'f','f','d','d','a','b'};
 
delay_init();     //???±??????????
NVIC_Configuration();// ?è????????????·?×é
uart_init(9600); //?®??????????9600
LED_Init();   //????????LED?????????????? 
 
while(1)
{
if(USART_RX_STA&0x8000)
{
      LED0=!LED0;
len=USART_RX_STA&0x3fff;//?????????????????????¤??
printf("\r\n?ú·???????????:\r\n");
for(t=0;t<len;t++)
{
USART1->DR=USART_RX_BUF[t];
while((USART1->SR&0X40)==0);//????·????á??
}
printf("\r\n\r\n");//????????
USART_RX_STA=0;
}else
{
times++;
if(times%200==0)
{
   for(t=1;t<7;t++)
{
USART1->DR=a[t-1];
while((USART1->SR&0X40)==0);//????·????á??
}
printf("\r\n\r\n");//????????
}
delay_ms(10);   
}
}  
}