When you select the Mode option as runtime switchable, the cmac_0_trans_debug module will be present in the example design. This cmac_0_trans_debug module is responsible for performing the DRP write operation to switch the transceiver operation mode, that is, CAUI-10 to CAUI-4/CAUI-4 to CAUI-10. When you set the switch_caui_mode input signal active-High for at least two clock cycles and then make it active-Low, it starts the DRP write operation for the transceiver common and transceiver channel and resets the 100G Ethernet subsystem. The state transition occurred during this process is shown in This Figure :
