App note from Abracon on measuring in circuit oscillator loop of most MCUs with internal amplifier unit to ensure proper operation. Link here
Growing technology trends including green energy initiatives and the explosive growth of IoT centric solutions, are driving the need to accurately define the frequency-selective network in order to achieve the best possible accuracy in frequency domain, while ensuring robust oscillator loop performance.
Measuring in-circuit crystal performance eliminates the problem by converting the unknowns into well knowns. Characterizing the complete frequency selective network including board parasitics minimizes uncertainty and maximizes confidence in long term system reliability.