The SetFeature request will be handled by the SIE in CY7C68001. You need to ensure that the SX2 is enumerated successfully by the external master. The EZ-USB SX2 is an SIE-only device. A master is required to tell SX2 to connect. SX2 is intended to be used in self-powered mode. Therefore, when the diagnostic driver is loaded by the operating system to run the test suite, the SX2 should still be running and be ready to test.