13.2.4.1.1 FIFO Under-Run Condition

If the transmit FIFO is accessed to transfer the data and there is no data in the FIFO, a transmit under-run error (TXUNDERRUN) is generated. This can be conditionally used to generate an interrupt. In this case, the transmission is assumed to have been lost and the application must catch the error and restart the transmission from the beginning. Internally, the transmit logic returns to an idle state and the entire transmission is deemed lost.