Many conflicting requirements typically exist in battery-powered applications. This is the reason for the flexible clocking system on the MSP430. It can support:

• Low clock frequency for energy conservation and time keeping

• High clock frequency for fast response times and fast burst processing capabilities

• Clock stability over operating temperature and supply voltage

• Low-cost applications with less-constrained clock accuracy requirements

The CS module addresses these conflicting requirements by allowing the user to select from the three available clock signals: ACLK, MCLK, and SMCLK. All three available clock signals can be sourced via any of the available clock sources (XT1CLK, VLOCLK, DCOCLK, or XT2CLK), giving complete flexibility in the system clock configuration. A flexible clock distribution and divider system is provided to fine-tune the individual clock requirements. The default internal oscillator (DCO), is set to run at 8 MHz, and this can easily provide 1 MHz system operation to the Main clock with a simple divider. The MODOSC module helps provide a custom 10 MHz clock source for some modules like the 10-bit ADC. As a failsafe, if clock accuracy is not a large concern, the device can run without any external crystals using the low voltage oscillator and the Modosc.