The XR21B1411 (B1411) is an enhanced Universal Asynchronous Receiver and Transmitter (UART) with a USB interface. The USB interface is fully compliant to Full Speed USB 2.0 specification that supports 12 Mbps USB data transfer rate. The USB interface also supports USB suspend, resume and remote wakeup operations.
The B1411 operates from an internal clock that is programmable to 6, 12, 24 or 48 MHz. Therefore, no external crystal / oscillator is required as in previous generation UARTs. With the fractional baud rate generator, any baud rate up to 12 Mbps can be accurately generated using the internal clock.
The large 128-byte TX FIFO and 384-byte RX FIFO of the B1411 help to optimize the overall data throughput for various applications. The Automatic Transceiver Direction control feature simplifies both the hardware and software for halfduplex RS-485 applications. If required, the multidrop (9-bit) mode with automatic half-duplex transceiver control feature further simplifies typical multidrop RS-485 applications.
The Vendor ID, Product ID, bus-powered mode, self-powered mode, remote wakeup support or maximum power consumption values, as well as default baud rate settings can be programmed using the on-board OTP through the USBD+ / USBD- pins.
The B1411 operates from a single 5V power supply and is available in a 16-pin QFN package.
Software drivers for Windows 2000, XP, Vista, 7, 8, and CE, as well as Linux and Mac are supported for the XR21B1411.
- ±15kV HBM ESD on USBD+/USBD-
- USB 2.0 Compliant Interface
- Supports 12 Mbps USB full-speed data rate
- Supports USB suspend, resume and remote wakeup operations
- Enhanced UART Features
- Data rates up to 12 Mbps
- Fractional Baud Rate Generator
- 128 byte TX FIFO
- 384 byte RX FIFO
- 7, 8 or 9 data bits
- 1 or 2 stop bits
- Odd, even, mark, space or no parity
- Automatic Hardware (RTS/CTS or DTR/DSR) Flow Control
- Automatic Software (Xon/Xoff) Flow Control
- Multidrop mode
- Auto Transceiver Control
- Half-Duplex mode
- Selectable GPIO or Modem I/O
- Internal 48 MHz clock with clock divisors programmable down to 6 MHz
- Single 5V power supply
- 16-pin QFN package
- Virtual COM Port Drivers
- Windows 2000, XP, Vista, 7, and 8
- Windows CE 4.2, 5.0, 6.0, and 7.0
- DAN-190, Exar UARTs in RS-485 Applications
- AN202, USB UART Board Design Considerations for USB Compliance
- AN205, Comparison of the XR21V1410 and the XR21B1411
- AN213, USB Basics for the Exar Family of USB UARTS
- AN217, Enumerating the XR21B1411 USB UART by Location in Windows
- AN-226, Windows Driver Customization for USB UARTs
- Portable Appliances
- External Converters (Dongles)
- Battery-Operated Devices
- Cellular Data Devices
- Factory Automation and Process Controls
- Industrial Applications
|Operating System||Driver Version||Release Date||File|
|Windows XP, Vista, 7, 8, 8.1, 10||188.8.131.52||December 2019|
|Linux 3.6.x and Newer||1C||January 2017|
|XRUSB1 for Win XP SP3 and newer||184.108.40.206||March 2016|
|Android Application||1C||November 2015|
|Linux 2.6.18 to 3.4.x||1A||January 2015|
|Sample USB UART GUI||220.127.116.11||December 2013|
Parts & Purchasing
|Part Number||Pkg Code||Min Temp||Max Temp||Status||Buy Now||Order Samples|
Active - the part is released for sale, standard product.
EOL (End of Life) - the part is no longer being manufactured, there may or may not be inventory still in stock.
CF (Contact Factory) - the part is still active but customers should check with the factory for availability. Longer lead-times may apply.
PRE (Pre-introduction) - the part has not been introduced or the part number is an early version available for sample only.
OBS (Obsolete) - the part is no longer being manufactured and may not be ordered.
NRND (Not Recommended for New Designs) - the part is not recommended for new designs.
Quality & Environmental Data
|Part Number||RoHS | Exempt||RoHS||Halogen Free||REACH||MSL Rating / Peak Reflow||Package|
|XR21B1411IL16-F||N||Y||Y||Y||L1 / 260ᵒC||QFN16 3x3|
|XR21B1411IL16TR-F||N||Y||Y||Y||L1 / 260ᵒC||QFN16 3x3|
Click on the links above to download the Certificate of Non-Use of Hazardous Substances.
Search our list of FAQs for answers to common technical questions.
For material content, environmental, quality and reliability questions review the Quality tab or visit our Quality page.
For ordering information and general customer service visit our Contact Us page.
Frequently Asked Questions
For some UARTs, Microsoft certified drivers are available for Windows Operating System and can be downloaded via Windows Update. These drivers and others, including for Linux and other Operating Systems can be found by visiting https://www.exar.com/design-tools/software-drivers Please note Software Driver Use Terms.
Click on the version link under Driver Version of the desired type of UART, part number and operating system. A zip file is downloaded which contains a ReadMe file with instructions.Links to datasheets and product family pages are in the software driver table for easy reference.
Find the product page of the part that you want to get an evaluation board for and click on Parts & Purchasing. Example:
Find the icons under Buy Now or Order Samples:
Click on the Buy Now icon and see who has stock and click on the Buy button:
Alternatively, you can click on the Order Samples
If the icons are missing, then contact Customer Support.
In this example, we looked for XRA1201. Click on part number header or on the link at the bottom of the result. This brings you to the product page. For example:
Click on Parts & Purchasing, highlighted with the blue arrow above. The screen changes to:
Notice the status column and the “Show obsolete parts” link. A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers, the legend still present:
Another method to find out if a part is OBS or EOL is to click on SUPPORT at the top:
And then Product Change Notifications:
Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:
If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.
1. Native drivers: Native drivers may be found in all major OS such as Windows, Linux, and Max OSX. Typically these drivers will be automatically loaded. In some cases, these are basic drivers and may have limitations on advanced device functionality, however. USB HID, Hub and CDC-ACM drivers are examples of native drivers. The CDC-ACM driver be used with our CDC-ACM class USB UARTs, but has limited functionality.
2. MaxLinear custom drivers: MaxLinear custom drivers may be used to support additional functionality in MaxLinear devices. For example, the MaxLinear custom driver for USB UARTs overcomes the limitations of the native CDC-ACM driver. See https://www.exar.com/design-tools/software-drivers for a list of and access to the drivers that we currently have. In some cases, the MaxLinear driver can also be customized, or source code can be provided after executing a Software License Agreement.
Yes: Go to the product page (XR22804 example below), click on the documentation tab on left, click on “Sample USB UART GUI” under Software:
The following lines of code must be modified in the xr_usb_serial_hal.c file in the xr_usb_serial_set_flow_mode function at the end of the function:
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, flow);
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, gpio_mode);
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0x3);
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);
xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0xB);
All of MaxLinear / Exar's USB UARTs are CDC class / CDC-ACM compliant, except for XR21B1421 which is an HID class device. This means they can use a native CDC driver. All major OS have native CDC drivers, except Windows prior to Windows 10.
None of the MaxLinear / Exar USB UARTs require their custom driver, however they will have certain limitations when not using it. The native CDC driver is not capable of accessing the internal memory map of any device. As a result, when using the native CDC driver, the device “defaults” to a particular configuration. The main implications of this default configuration are that hardware RTS/CTS flow control is enabled and that other settings / advance settings are not configurable. Some devices, for example the XR21B1411 which has an internal OTP memory, can be programmed to change this default configuration, but the configuration cannot be changed “on the fly”.
Submit a Technical Support Question As a New Question