It is important to start the test procedure with all connections to the TUSB21XX device disconnected and no test packets being sent from the host. Doing so will ensure high-speed signal compensation is active throughout the test. The host mode test procedure is as follows:

1. Connect TUSB21XX input to host (test packet source).
2. Toggle RSTN (reset) on TUSB21XX.
3. Connect TUSB21XX output to oscilloscope/measurement tool.
4. Send high-speed test packets via xHCI Electrical Test Tool (Figure 2-2).

Figure 2-2 Host Mode Testing Software Configuration

Once test packets have been sent via software, the scope output and status flags should be observed as below. The high-speed enable (ENA_HS) flag switches high during the first test packet and remains that way for the duration of testing (Figure 2-3).

Figure 2-3 Host Mode Enable High-Speed (ENA_HS) Status Flag

The connection-detected (CD) flag remains low during all steps of testing (Figure 2-4).

Figure 2-4 Host Mode Connection-Detected (CD) Status Flag