XR22801 Datasheet, PDF (8/42 Pages) Exar Corporation – Hi-Speed USB to 10/100 Ethernet Bridge

XR22801
Functional Description
USB Interface
The XR22801 is a USB compound device with an embedded hub and 4 downstream functions. The downstream functions
of the XR22801 are 10/100 Ethernet, a UART function, an I²C function, and an Enhanced Dedicated GPIO Entity (EDGE)
function. The upstream USB interface of the XR22801 is compliant with both USB 2.0 full and hi-speed specifications. All
functions downstream of the hub are hi-speed functions.
The XR22801 will have a single vendor ID and vendor string. Each function in the XR22801 will have an individual product
string and serial string. The default serial number strings will be based upon the uniquely assigned Ethernet MAC address
for each XR22801 device. The serial strings for multiple functions within the same device will differ only by a single charac-
ter which will be assigned a value between 0 and 7. All string and ID values can be overridden via OTP.
The XR22801 can be placed into a low power or suspended state by the USB host. By default the XR22801 hub is config-
ured for bus powered mode with a maximum power of 250 mA. All other functions in the XR22801 are configured for self-
powered mode. In bus powered mode, the Ethernet Phy must be powered down during suspended state to meet USB sus-
pend power requirements. The Ethernet Phy may remain enabled to support Ethernet remote wakeup during suspend if the
device is self-powered and the OTP is modified to report the hub function as self-powered in the USB descriptors. See
Ethernet Remote Wakeup section on page 10.
Each function of the XR22801 supports one configuration and utilizes the following USB endpoints:
• USB hub
• Control endpoint
• Interrupt-in endpoint
• Ethernet function
• Control endpoint
• Interrupt-in endpoint
• Bulk-in and bulk-out endpoints
• I²C function
• Control endpoint
• Interrupt-in and interrupt-out endpoints
• EDGE Controller function
• Control endpoint
• Interrupt-in and interrupt-out endpoints
• UART function
• Control endpoint
• Interrupt-in endpoint
• Bulk-in and bulk-out endpoints
USB Vendor ID
Exar’s USB vendor ID is 0x04E2. This is the default vendor ID that is used for the XR22801. Companies may obtain their
own vendor ID, by becoming members of USB.org. The XR22801 OTP can then be modified to report this vendor ID in the
USB descriptors.
USB Product ID
Each function in the XR22801 has an individual USB product ID. The default product IDs for each of the functions are
shown in Table 1. These values can be modified by programming the OTP. Companies using their own vendor ID may also
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