Here the possibilities of clocking the MSP430 with the basic clock are shown. The MSP430 can be run without a crystal because the DCO, the on-chip oscillator, functions completely independently from the crystal oscillator. The lower left shows the most common application of using the 32768 crystal for the low power A Clock signal. The DCO can also be sourced through an external resistor called ROSC. In this case, the external resistor allows a current to be injected into the DCO, controlling its frequency and reducing its temperature drift.