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Initial handshake and speed detection | Cypress Semiconductor

Initial handshake and speed detection

Summary: 1 Reply, Latest post by scutifer on 07 Jan 2015 01:33 AM PST
Verified Answers: 0
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Cletus's picture
7 posts

Does anyone have a good reference on the entire handshake process for an FX3 device?  We're trying to track down enumeration issues - frequent failures to detect a device, and a USB 3.0 interface that always fails to enumerate as USB 3.0 and falls back to 2.1.  The USB event log used in the USBBulkSourceSink image shows the following, but I need a better understanding of the exact sequence of events that occur between "attempted again" and "disabled".  I have protocol analyzer traces of the sequence, but still lack a deeper understanding of what is happening and why.




/* Indicates that a USB 3.0 connection is being attempted again. */



/* Indicates that the USB High-Speed handshake has been completed. */



/* Indicates that USB 3.0 Rx Termination has been detected. */



/* Indicates that the USB 3.0 link has been disabled. */


scutifer's picture
Cypress Employee
134 posts

The enumeration process would that the device tries SuperSpeed enumeration 3 times and then falls back to USB 2.0. The failures you see could be because of a bad cable, impedance mismatch on the trace, bad power supply etc. As a first step, make sure that your board is designed according to the guidelines in AN70707 (


And if you can take a bus trace with a hardware analyser like a LeCroy or a Beagle or an Ellisys, please do so and attach it here (or mail it over to Tech Support).

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