The XR21B1422 is an enhanced Universal Asynchronous Receiver and Transmitter (UART) bridge to USB interface. The USB interface is fully compliant to the USB 2.0 (Full-Speed) specification with 12 Mbps USB data transfer rate. The USB interface also supports USB suspend, resume and remote wakeup operations. The USB Vendor ID, Product ID, power mode, remote wakeup support, maximum power, and numerous other settings may be programmed in the on-chip OTP memory via the USB interface.
The XR21B1422 includes an internal oscillator and does not require an external crystal/oscillator. Any UART baud rate up to 12 Mbps may be generated with this internal clock and the fractional baud rate generator.
The UART pins for each port may also be configured as GPIO; direction, state, output driver type and input pull-up or pull-down resistors are programmed either through on chip OTP, or on the fly via memory mapped registers.
Large 512-byte TX and RX FIFOs prevent buffer overflow errors and optimize data throughput. Automatic half-duplex direction control and optional multi drop (9-bit) mode simplify both hardware and software in half-duplex RS-485 applications.
The XR21B1422 uses the native OS CDC-ACM driver or an Exar supplied custom driver. Exar provides WHQL/HCK-certified software drivers for Windows 2000, XP, Vista, 7, 8, 8.1 as well as software drivers for Windows CE, Linux and Mac OS X. Full source code is available.
The XR21B1422 operates from a single 5V or 3.3V power supply. When powered with 5V input, a regulated 3.3V output is supplied.
For UART technical support or to obtain an IBIS model for this product, please email Exar's UART Technical Support group.