38.9.1.1 TX FIFO Status Flags

There are three transmit status flags:
  • TFEIF (TFERFFIF): Transmit FIFO Empty Interrupt Flag; set when the FIFO is empty.
  • TFHIF (TFHRFHIF): Transmit FIFO Half Empty Interrupt Flag; set when FIFO is less than half full.
  • TFNIF (TFNRFNIF): Transmit FIFO Not Full Interrupt Flag; set when FIFO is not full.

The status flags of a transmit FIFO are set when there is space to load a new message object into the FIFO. Before the first message object is loaded (after the FIFO is reset), all status flags are set. When the FIFO is fully loaded, all flags are cleared.