The Unified Program and Debug Interface (UPDI) is a Microchip proprietary interface for external programming and on-chip debugging of a device. It is a successor to the PDI 2-wire physical interface, which is found on all AVR XMEGA devices. UPDI is a single-wire interface providing a bidirectional half-duplex asynchronous communication with the target device for purposes of programming and debugging.
When designing an application PCB, which includes an Microchip AVR with the UPDI interface, the pinout shown below should be used. One of the 6-pin adapters provided with the Power Debugger kit can then be used to connect the Power Debugger probe to the application PCB.
Figure 1. UPDI Header Pinout