Arduino Zero Serial Interface (UART) Speed

For Arduino Zero board with ATMEL SAMD21G18 Microcontroller, what is the maximum speed or baud rate for its serial (UART) Interface?

I looked at the data sheet for this MCU and according to the baud-rate calculation Table (attached) with an internal clock speed of 48Mhz, it shows it can support up to 3Mbps… is this number correct? does any one try this baud rate with the MCU?

Connecting to what? If you're going through the EDBG onboard usb/serial port, that's documented as having a max baud rate of 2Mbps. (http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-42096-Microcontrollers-Embedded-Debugger_User-Guide.pdf)

The Arduino code uses a relatively trivial algorithm to set the uart baud rate; I don't see any reason that it wouldn't support the full speed listed in the datasheet. Note that running async comm at 3Mbps is a bit risky from a hardware/drive/wiring perspective...