4.3 Connection for RESET

The RESET pin on the device is active-low with an internal pull-up resistor, and externally pulling the pin low will result in a device Reset. An external pull-up resistor is usually not required.

The following figure shows the recommendation for connecting an external Reset switch to the device.

Figure 4-3. Recommended External Reset Circuit Schematic

Shorting the filtering capacitor may cause a noise spike that can harm the system. To prevent this, a resistor in series with the switch can safely discharge the filtering capacitor preventing a current surge.

UPDI Enable with High-Voltage Override

It is possible to enable a disabled UPDI by applying a high-voltage pulse on the RESET pin. Take care with the reset circuit design and any components connected to the RESET pin to prevent damage if such a high-voltage pulse may be applied.

See the Connection for UPDI Programming sub-section and the UPDI section for more details.