Xplained Mini Clock Output

The mEDBG outputs its CPU clock on a pin. This clock pin is connected to the ATmega168PB clock input and is used to have a synchronous clock with the mEDBG to enable debugging through debugWIRE.

To disconnect the external clock to the ATmega168PB, a 0Ω resistor or strap has to be removed from the footprint, as shown in the figure below (R109).
Figure 1. External Clock Footprint

The mEDBG CPU clock frequency depends on the selected voltage, see the table below.

Table 1. CPU Clock vs. Voltage
Target Voltage mEDBG CPU Clock
3.3V 8 MHz
5.0V 16 MHz