A 1-bit flag that transitions from 0 to 1 to indicate the data transmit register (DXR) contents have been copied to the data transmit shift register (XSR) and that data is ready to be loaded with a new data word. A transmit interrupt (XINT) is generated upon the transition.

The XRDY bit can be polled in software instead of using serial port interrupts. This bit is stored in the serial port control register (SPC) and TDM serial port control register (TSPC).