37.2.4 Physical Layer

The PHY layer is the communication interface between a connected programmer/debugger and the device. The main features of the PHY layer can be summarized as follows:

• Dedicated pin on the device with no other function
• Support for UPDI One-Wire mode, using asynchronous, half-duplex UART communication on the UPDI pin
• Internal baud detection, clock and data recovery on the UART frame
• Error detection (parity, clock recovery, frame, system errors)
• Transmission response generation (ACK)
• Generation of error signatures during operation
• Guard time control