[192] CLOCK: LFRC frequency offset after calibration

This anomaly applies to IC Rev. Rev 1, build codes QFAA-B00, QFAB-B00, CIAA-B00.

It was inherited from the previous IC revision Engineering C.

Symptoms

LFRC oscillator frequency is wrong after calibration, exceeding 500 ppm.

Conditions

On some devices, when entering System ON Idle while calibration is ongoing.

Consequences

After calibration, LFRC has a frequency offset that is outside specification.

Workaround

Apply the following code before starting the RCOSC32K calibration:

*(volatile uint32_t *)0x40000C34 = 0x00000002; 
Apply the following code after the RCOSC32K calibration is finished:

*(volatile uint32_t *)0x40000C34 = 0x00000000;
This workaround is included in SDK v15.0.0 and SoftDevices S140, S132, and S112 v6.0.0.