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USB System Architecture (USB 2.0).pdf
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Chapter 11: The High-Speed Signaling Environment

Figure 11-4: Chirp Sequence Used to Detect High-Speed Capable Device

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High-Speed Interfaces Idled

Once the Chirp sequence ends the bus is in the idle state. Both data lines are held low via the full-speed drivers that continuously signal SE0 to provide impedance matching to support high-speed differential signaling. (See “Impedance Matching” on page 224.) This also dictates several changes from the fullspeed signaling environment for events that used SE0, including RESET and EOP.

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