Please try the below steps to enable Ethernet flow control: 1) Set MACCFG1[Rx_Flow] && MACCFG1[Tx_Flow] to 1 2) Set RCTRL[LFC] to 1. Setting the flow control bits Rx_Flow and Tx_Flow means that the MAC can detect and act on PAUSE flow control frames, receive and transmit respectively. There are two ways you can confirm or see them in action: 1) Software sending a PAUSE frame through TCTRL[TFC_PAUSE] 2) Changing some hidden FIFO threshold registers, such that the FIFO is about to overflow and that triggers eTSEC logic to send a PAUSE.