Where is the Oscillator Stop (OS) status bit in PCF85263A RealTimeClock? The Data Sheet talks at length about the bit, but I cannot find it in the control registers. Access to bit is critical to insure the oscillator has not been interrupted - even for a moment. My design uses super capacitor for backup (and internal switch), but backup voltage can go too low for oscillator to keep functioning. Attached are two relevant pages of data sheet.