Even though there is an onboard debugger, external debuggers can be connected directly to ATmega4809 Curiosity Nano to program/debug the ATmega4809. The onboard debugger keeps all the pins connected to the ATmega4809 and board edge in tri-state when not actively used. Therefore, the onboard debugger will not interfere with any external debug tools.
Figure 1. Connecting the PICkit™ 4 to ATmega4809 Curiosity Nano
Figure 2. Connecting the Atmel-ICE to ATmega4809 Curiosity Nano
To avoid contention
between the external debugger and the onboard debugger, do not start any
programming/debug operation with the onboard debugger through Atmel
Studio/Microchip MPLAB® X or mass storage programming while
the external tool is active.