This scope trace shows the on-demand clock system of the MSP430. The two traces shown are of an external interrupt coming into an MSP430 and of the DCO clock system output from the MSP430. Looking closely it can be seen that prior to the interrupt falling edge, the DCO is off (the MSP430 is in a low-power state). A short time after the interrupt edge falls, the DCO begins clocking and the CPU becomes active. There are two interesting features about this plot that should be looked at in greater detail. First, the delay time between the falling interrupt edge and the startup of the DCO is 204 nanoseconds, essentially making this an instant-on clock. Secondly, the very first cycle of the DCO is at the correct frequency and is stable and usable for processing and timing. This instant-on clock capability of the MSP430 enables seamless movement throughout the low-power modes and enables the user to minimize the active application time.