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How are EHCI and OHCI of the USB host controller switched?

Latest Updated:08/01/2005

Question:

How are EHCI and OHCI of the USB host controller switched?

Answer:

Renesas Electronics' host controller automatically detects the transfer speed of the connected devices.
Prior to USB device connection, EHCI is the owner of each port. When a USB device is connected, the transfer speed of the connected device is automatically detected in the sequence laid out in the USB 2.0 standard.

The uPD720100A notifies the system about whether the connected device is an HS or FS/LS device, and if it is a FS/LS device, it switches over to OHCI (actually, this control is performed jointly with the driver).
In other words, the uPD720100A checks the connected device. If the connected device is an HS device (FS/LS device), EHCI (OHCI) becomes the owner of the port in question.

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