The address swap module can be enabled for use on the loopback path. This would allow the example design, targeted to a suitable board, to be connected to an Ethernet protocol tester. The address swap module waits until both the DA and SA have been received before starting to send data to the TX FIFO.
If enabled, the module swaps the destination and source addresses of each frame as shown in the previous figure. To ensure that the outgoing frame destination address matches the source address of the link partner, otherwise the DA and SA are left untouched. The module transmits the frame control signals with equal latency to the frame data.