Does the BL652 use a different clock source than internal RC oscillator?

Answer

The 32MHz crystal inside the BL652 is for the High speed oscillator. For the 32.768kHz (low speed clock) we use the RC oscillator inside the chipset.  Users also have the option to use an external 32.768kHz crystal. For more information, please see page 44, section 5.2 of the Datasheet.