Multiple oscillators are utilized to provide both an ultra-low power standby mode and “on-demand” high-performance processing. The flexible clock system allows the MSP430 to operate optimally from a single 32kHz crystal sourcing an always on low frequency Auxiliary Clock (ACLK) with no additional external components. The ACLK enables the MSP430’s ultra-low-power standby mode (LPM3) and an embedded real-time clock function. Optionally, the new embedded 12kHz internal very-low power oscillator (VLO) on the all MSP430F2xx (except the F21x1) and on the future F5xx families can be used to source the ACLK. In LPM3, the MSP430 typically consumes less than 1µA.