This can be shared only when TXOUTCLK (and hence gtrefclk) of both instances are synchronous;otherwise this should be connected to the TXOUTCLK port of the same instance (For 1G mode). This clock frequency is 62.5 MHz in 1 Gbps mode, 156.25 MHz in 2.5 Gbps mode. This clock canbe used across the whole device and is used for any GT that has the same gtrefclk