xr21b1411 Exar Corporation, xr21b1411 Datasheet - Page 9

• Manufacturer Part Number: xr21b1411
• Description: Enhanced 1-ch Full-speed Usb Uart
• Manufacturer: Exar Corporation

XR21B1411
ENHANCED 1-CH FULL-SPEED USB UART
REV. 1.1.0
1.3.9
Remote Wakeup
If the B1411 device has entered the Suspend state, the GPIO0/RI# pin can be used to request that the host exit
the Suspend state. A high to low transition on this pin will cause the device to signal a remote wakeup request
to the host via a custom driver. Note that the standard CDC-ACM driver does not support this feature.
In order for the remote wakeup to work, several things must be properly configured. First, the GPIO0/RI# pin
must be configured as an input. Additionally, the B1411 device must have the remote wakeup feature support
indicated in the USB attributes -
See ”Section 3.2.1.11, USB_ATTRIBUTES (Read / Write OTP)” on
page 25.
Lastly, the host must detect the B1411 support for remote wake up and enable this feature. Note
that per USB standard, any remote wakeup signaling to the host will be suppressed for the first 5 ms after the
device enters the suspend state.
1.4
OTP
The OTP is an on-chip non-volatile memory, that is incrementally one-time programmable via the USB
interface. The OTP is divided into 2 portions. The lower half, from address 0x0 to 0xFF has an unprogrammed
state of 0x00. The upper half from locations 0x100 to 0x1FF has an unprogrammed state of 0xFF. Bit
locations within the memory may be programmed at various times allowing for customization of the B1411
UART device. Some bits are pre-programmed at the factory and caution must be taken not to program any
locations except those user defined addersses given in this data sheet.
The OTP memory contains user programmable locations for customer vendor and product ID and device
attributes.
Table 11
lists all of the OTP memory contents.
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