STM32FC8T6的串口3能用吗

哪位用过STM32FC8T6的串口3，因为需要串口较多，需要用到串口三，不知与其它串口配置有什么不同，通信不上，串口1和2都可以，哪位用过
void USART3_Initialise( u32 bound )
{
    GPIO_InitTypeDef GPIO_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    USART_InitTypeDef USART_InitStructure;
  /* Enable the USART3 Pins Software Remapping */
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB ,ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
/* Configure USART3 Rx (PB.11) as input floating */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/* Configure USART3 Tx (PB.10) as alternate function push-pull */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/* Enable the USART3 Interrupt */

NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 4;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
USART_InitStructure.USART_BaudRate = bound;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART3, &USART_InitStructure);
USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
USART_Cmd(USART3, ENABLE);
}
// USART3DATA[20]=0;
void USART3_IRQHandler(void)                             //′??ú?D??ê?è?
{
static u8 i = 0;
u8 data = 0;
      if(USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == SET)
      {
       data = USART_ReceiveData(USART3);
    //i++;
    //if(i == 9)
     //{
     //i = 0;
     //temp1 = 1;     
         
       // }
        USART_SendData(USART3, data);
    }
}

先确定下有没有串口3的功能，再就是管脚有没有复用