The Serial Wire Debug (SWD) interface provides a non-intrusive mechanism for debugging and tracing nRF9160. It can also be used for programming the firmware and accessing registers.

The SWD interface consists of SWDCLK (pin 33) and SWDIO (pin 34). The SWDCLK pin provides clock signal, and SWDIO provides data. The SWDIO pin has an internal pull-up resistor whereas the SWDCLK pin has an internal pull-down resistor. The SWD interface's logic level high originates from the VDD_GPIO level. For more information on the SWD interface, see Debug and trace in nRF9160 Product Specification and nRF9160 Hardware Verification Guidelines.