TMS320F280037: CAN message interrupts -- RX works, TX not

Hey folks,

I am now working with a TMS320F280037 board and using its CAN bus for communication. 

In the application, I have multiple TX, and RX message objects setup in main, something like 

CAN_initModule(CANA_BASE);

CAN_setBitRate(CANA_BASE, DEVICE_SYSCLK_FREQ, 500000, 20);

CAN_enableInterrupt(CANA_BASE, CAN_INT_IE0 | CAN_INT_ERROR |CAN_INT_STATUS);

...

Interrupt_register(INT_CANA0, &canaISR);
    
Interrupt_enable(INT_CANA0);
CAN_enableGlobalInterrupt(CANA_BASE, CAN_GLOBAL_INT_CANINT0);

// TX message object, # 1
CAN_setupMessageObject(CANA_BASE, 1, 0x111,
                           CAN_MSG_FRAME_STD, CAN_MSG_OBJ_TYPE_TX, 0,
                           CAN_MSG_OBJ_TX_INT_ENABLE, 8);

// TX message object, # 2
CAN_setupMessageObject(CANA_BASE, 2, 0x112,
                           CAN_MSG_FRAME_STD, CAN_MSG_OBJ_TYPE_TX, 0,
                           CAN_MSG_OBJ_TX_INT_ENABLE, 8);

// RX message object, # 3
CAN_setupMessageObject(CANA_BASE, 3, 0x101,
                       CAN_MSG_FRAME_STD, CAN_MSG_OBJ_TYPE_RX, 0,
                       CAN_MSG_OBJ_RX_INT_ENABLE, 8);
                       
CAN_startModule(CANA_BASE);

and in the canaISR, I defined the action when each of the events (Transmission and receive interrupts) happens, something like

__interrupt void canaISR(void)
{
    uint32_t intr_status;
    uint32_t can_status;

    //
    // Read the CAN-B interrupt status to find the cause of the interrupt
    //
    intr_status = CAN_getInterruptCause(CANA_BASE);

    //
    // If the cause is a controller status interrupt, then get the status
    //
    switch (intr_status) {
    case CAN_INT_INT0ID_STATUS:
    {
        //
        // Read the controller status.  This will return a field of status
        // error bits that can indicate various errors.  Error processing
        // is not done in this example for simplicity.  Refer to the
        // API documentation for details about the error status bits.
        // The act of reading this status will clear the interrupt.
        //
        can_status = CAN_getStatus(CANA_BASE);

        break;
    }

    case 3: // the RX message object # (which is 3)
    {
        // ... application codes

        CAN_clearInterruptStatus(CANA_BASE, 3);

        break;
    }


    case 1: // TX message object: 1
    case 2: // TX message object: 2
    {
        // basically nothing to do here just clear the status
        CAN_clearInterruptStatus(CANA_BASE, intr_status);
        break;
    }

    default:
    {
        //
        // Spurious interrupt handling can go here.
        //
        break;
    }

    } // end-switch

    //
    // Clear the global interrupt flag for the CAN interrupt line
    //
    CAN_clearGlobalInterruptStatus(CANA_BASE, CAN_GLOBAL_INT_CANINT0);

    //
    // Acknowledge this interrupt located in group 9
    //
    Interrupt_clearACKGroup(INTERRUPT_ACK_GROUP9);
}
/************************CAN ISR**********************/

Now my observation is, the RX interrput gets correctly operated (the application codes in the RX switch case lines are operated, adding breakpoints it will stop there when a message was received). But the TX interrupt seems not happeing. Adding breakpoint in the TX Messag object switch case lines within canaISR, but not getting triggered.  

I am expecting the TX interrupt to work properly since I have setup the TX message objects as CAN_MSG_OBJ_TX_INT_ENABLE. The RX message objects are setup in a similar manner (using CAN_MSG_OBJ_RX_INT_ENABLE) which works well, so I don't understand why the TX message objects have issue here.

Appreciate for replies and advices.

Regards,

Wei