LAN8810 - TXCLK Pin State During 1000BASE-T Operation
From "Table 2-1: GMII Interface Pins" of the LAN8810 datasheet, TXCLK is not used in 1000BASE-T mode. It has VO8 buffer type. VO8 means variable voltage output with 8 mA sink, and 8 mA source. The TXCLK is driven high or low depending on the clock output state when the auto-negotiation resolved to 1000BASE-T mode.