Nordic Thingy:91™ is equipped with one programming and debugging interface connector (P8) that is shared between the nRF9160 and nRF52840.
The device to be programmed is selected by the SWD SELECT switch (SW2). The selection of device can also be controlled by connecting TP28 to 1.8 V or ground.
Figure 1. SWD SELECT switch
The SWD interface of the nRF9160 can also be connected to the nRF52840. The enabling of this connection is controlled by the nRF52840.
Figure 2. SWD interface and control schematic
