XR22801 Datasheet, PDF (9/42 Pages) Exar Corporation – Hi-Speed USB to 10/100 Ethernet Bridge

XR22801
select their own product IDs. Additionally, upon request Exar will provide a selection of different product IDs for use with
Exar’s vendor ID for companies that do not wish to become members of USB.org, but wish to use their own product ID.
Table 1: Default XR22801 Product IDs
XR22801 Function
Hub
Ethernet 10/100
UART
I²C
EDGE
Default Product ID
0x0801
0x1300
0x1400
0x1100
0x1200
USB Suspend
All USB peripheral devices must support the USB suspend mode. Per USB standard, the XR22801 device will begin to
enter the suspend state if it does not detect any activity, (including Start of Frame or SOF packets) on its USB data lines for
3 ms. The peripheral device must then reduce power consumption from VBUS power within the next 7 ms to the allowed
limit of 2.5 mA per function for the suspended state. Because the XR22801 is a compound device with 5 functions, the sus-
pend state power limit is 12.5 mA for the device. Note that in this context, the "device" is all circuitry (including the XR22801)
that draws power from the host VBUS.
Remote Wakeup
When the XR22801 is suspended, the E0/RI#/RWK#/G0 pin may be used to request that the host exit the Suspend state if
it is configured as an input. A high to low transition on this pin will cause the device to signal a remote wakeup request to the
host via Exar’s custom driver. Note that the CDC-ACM driver does not support the remote wakeup feature. The E0/GPIO0/
RI#/RWK# pin may be used to signal remote wakeup by default. Additionally, the E6/RX/RWK# pin, if configured as an
input, may also be used for remote wakeup if enabled using the REMOTE_WAKEUP register. The Ethernet function in the
XR22801 can also be used for remote wakeup under certain conditions. Refer to Ethernet Remote Wakeup on page 10.
USB Strings
USB specifies three character string descriptors that are provided to the USB host during enumeration in string descriptors:
the manufacturer, product and serial strings. In a compound device such as the XR22801, each function provides these
strings to the USB host. The default manufacturer string for the XR22801 device is "Exar Corp.". The default product strings
for the hub, Ethernet function, UART function, I²C function and EDGE function are shown in Table 2. The serial number
string is a unique alpha-numeric ASCII string programmed into the device at the factory.
Table 2: Default XR22801 Product Strings
XR22801 Function
Hub
Ethernet 10/100
UART
I²C
EDGE
Default Product String
Exar’s XR22801 Hub
Exar USB Ethernet
Exar USB UART
Exar USB I2C
Exar USB EDGE
The OTP may be used to override these strings. However, to ensure unique serial numbers for each device, it is recom-
mended that the factory pre-programmed serial number string be used and not be overwritten via OTP.
© 2015 Exar Corporation
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