The TUSB2E221 features three additional pins for repeater control and functionality, the RESETB, VIOSEL, and CROSS pins.

The VIOSEL pin is used to control the voltage thresholds of the IO pins (EQ, CROSS, INT, SDA/SCL, RESETB) depending on how it is configured. For 1.8V high IO signaling, the VIOSEL pin should be pulled-up to 1.8V. For 1.2V high IO signaling, the VIOSEL pin should be pulled down to VSS/GND.

The RESETB pin is an active low reset that controls whether the TUSB2E221 is enabled or not. When the RESETB pin is pulled low, the TUSB2E221 will be disabled and have no functionality, disabling the USB2 lane. When the RESETB pin is pulled high, the TUSB2E221 will be enabled and place the eUSB2 PHYs into default mode, waiting for configuration from the eDSPr or eUSPr. We typically recommend pulling the RESETB pin up to the VIO selected by the VIOSEL pin with a 1Kohm resistor, with a 100nF cap connecting to GND.

Finally, if the DSBGA package of the TUSB2E221 is being used, there will be an additional CROSS pin which controls an internal crossbar mux inside the TUSB2E221. This internal mux controls the routing of the DP/DN A/B ports, and the eDP/eDN 0/1 ports. If the CROSS pin is pulled low at startup, eUSB0 will route to USBA, and eUSB1 will route to USBB. If the CROSS pin is pulled high at startup, eUSB0 with route to USBB, and eUSB1 will route to USBA. In most cases where this crossbar mux isn't needed, it's best to leave the CROSS pin pulled-down and route the signals across the repeater. For the QFN package of the TUSB2E221, this mux is not accessible and is pulled-down by default.