The RTCC and DSWDT need a clock source to operate. When using the 31 kHz internal RC oscillator as a clock source, no external circuitry is required. For more timing accuracy, an external 32.768 kHz crystal can be connected to the microcontroller’s secondary oscillator pins (as shown in the example circuit). To achieve low-power consumption for Deep Sleep applications, the secondary oscillator has very low drive levels. The downside is increased sensitivity to rapidly changing signals in close proximity. Locate the crystal and capacitors as close to the microcontroller as possible and avoid routing signals, other than VSS and VDD, near the oscillator circuit.