Universal Serial Bus OTG Controller
UG0331 User Guide Revision 15.0 291
For more information on USB 2.0 PHY interfaces refer to the following links:
• www.ulpi.org
• www.ulpi.org/ulpi_whitepaper_v2.pdf
• www.ulpi.org/documents.html
• www.ulpi.org/utmiplus_whitepaper.pdf
• www.usb.org/developers
10.2.3 USB OTG Controller Operations
This section describes the following:
• Modes of USB OTG Controller Operation
• USB OTG Controller: Reset Operations
• USB OTG Controller: Suspend/Resume Operations
• USB OTG Controller: Connect/Disconnect Operations
10.2.3.1 Modes of USB OTG Controller Operation
The USB OTG Controller in SmartFusion2 device can be used in the following three modes:
10.2.3.1.1 USB Host Mode
In this mode, the USB OTG controller acts in a USB host function. As the USB protocol is host driven, the
USB host is completely responsible for all the transactions in the bus. In this mode, the USB OTG
controller enumerates the external device that is connected. Based on the USB firmware, class drivers,
and application code implemented in the SmartFusion2 device; if the connected device USB class is
supported, the SmartFusion2 USB OTG controller exchanges the data with the connected device, as per
the application requirement of the USB function.
The USB multi-point capability of USB controller is associated with a range of registers (Table 297,
page 358). These registers are needed to record the allocation of device functions to individual controller
endpoints, and device function characteristics such as; endpoint number, operating speed, and transaction
type on an endpoint-by-endpoint basis. Although principally associated with the use of the core as the host
to a number of devices, these registers are also required to be set when the core is used as the host for a
single device.
The following figure shows the flow chart of the overall operation in the USB Host mode.
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