stm8s208 can时间触发模式的问题

需要发送一个标准数据帧，DLC为8，使用下面函数开启时间触发通讯模式，串口打印确认TTCM和TGT位置1，而且发送时间戳寄存器有数据变化，但是没有发出时间戳。

void CAN_TTComModeCmd(FunctionalState NewState)

{

CAN_Page_TypeDef can_page = CAN_GetSelectedPage();

/ Check the parameters /

assert_param(IS_FUNCTIONALSTATE_OK(NewState));

if (NewState != DISABLE)

{

/Enable the TTCM mode /

CAN->MCR |= CAN_MCR_TTCM;

/Set TGT bits setting in Tx and FIFO pages/

CAN->PSR = CAN_Page_TxMailBox0;

CAN->Page.TxMailbox.MDLCR |= CAN_MDLCR_TGT;

CAN->PSR = CAN_Page_TxMailBox1;

CAN->Page.TxMailbox.MDLCR |= CAN_MDLCR_TGT;

CAN->PSR = CAN_Page_TxMailBox2;

CAN->Page.TxMailbox.MDLCR |= CAN_MDLCR_TGT;

CAN->PSR = CAN_Page_RxFifo;

CAN->Page.RxFIFO.MDLCR |= CAN_MDLCR_TGT; }