The clock block of the F1680 Series has a main system clock using an Internal Precision Oscillator (IPO). This IPO is a trimmable clock source which requires no external components, is frequency selectable from one of eight frequencies (43 kHz to 11.0592 MHz), and is available with factory-trimmed calibration data. There is also a secondary low power 32 kHz Oscillator which is optimized for use with a 32 kHz watch crystal that can be used as timer/counter clock source in any mode.