How to clear CAN TX flag CANTFLG.TXE to indicate the message buffer is full after a FIFO write done?

[007]

Hello, the CAN Transmit Buffer Empty flag CANTFLG.TXE is set to 1 to clear it, after a write FIFO done to start the transmission, is that? Because from the example code below, after the TX FIFO is filled, CANTFLG = TxbufSel, at this time, TxbufSel is read from CANTBSEL, the bit of selected FIFO should be set.

byte CanTxFrame(CanMsg_t msg)

{  

    byte TxbufSel;        

    byte idx;           // Index to data within the transmission buffer

    if (!CANTFLG)       // Retrun if Transmit Buffer is full

        return ERR_BUFFER_FULL;

    CANTBSEL = CANTFLG; // Select lowest empty buffer

    TxbufSel = CANTBSEL; // Backup selected buffer

    *((word *) ((word)(&CANTXIDR0)))= msg.ID<<5;   // 11bit ID, RTR=0: data frame; IDE=0

// Load data to Data Segment Registers

    for (idx=0; idx<(msg.DtLen); idx++) {

        *(&CANTXDSR0 + idx) = (msg.data)[idx]; 

    }

    CANTXDLR  = msg.DtLen;   // set Data Length Code

    CANTXTBPR = 0;           // set highest priority

    CANTFLG = TxbufSel;      // Start transmission

    while ( (CANTFLG&TxbufSel) != TxbufSel);  // Wait for Transmission completion

    return NO_ERR;

}

[kef2]

Yes, to start transmision you need to clear one of CANTFLG flags.

To fill Tx message buffer, you need to first map one of Tx buffer to address bus. This is what CANTBSEL register is used for. Even if you write 7 to CANTBSEL, only one CANTBSEL bit will read back as set at once, and only 1 out of 3 buffers can be mapped to address bus.

To send selected CANTBSEL buffer, you may just copy CANTBSEL to CANTFLG. Intermediate variable TxbufSel is not required.

[007]

got it, thank you !