Running the MSP430 at a crystal frequency other than 32.768kHz

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Running the MSP430 at a crystal frequency other than 32.768kHz [Copy link]

The MSP430x3xx devices are designed to use a 32kHz watch crystal and then generate an internal high-speed master clock (MCLK) from a separate, internal digitally controlled oscillator (DCO). The MCLK automatically stabilizes in the MSP430x3xx devices to a user-programmed value using an internal frequency-locked loop (FLL) circuit. The MSP430x1xx and MSP430x4xx devices have a crystal oscillator that accepts either a 32kHz or high-speed crystal. Some MSP430x1xx and MSP430x4xx have an additional crystal oscillator that accepts only high-speed crystals. This allows one or both crystals to be connected simultaneously, with each crystal used only when necessary. The MSP430x1xx and MSP430x4xx devices also have a programmable internal DCO that can generate a high-speed clock independent of any crystal. In the MSP430x4xx devices, the FLL can also stabilize the DCO based on many external 32kHz crystals similar to the MSP430x3xx devices. For specific features and functions of the different clock circuits and devices, refer to the datasheet and user guide. About Sink and Source Currents of MSP430 I/O Pins The MSP430 does not specify the absolute maximum current from the I/O pins. For the Voh and Vol specifications, refer to the datasheet. It is shown that each I/O pin can provide a few milliamps of current, but the output voltage will change with increasing current. The footnotes to these specifications usually give the maximum total current that all the outputs combined can provide to maintain a specific voltage. The MSP430 I/Os are not suitable for driving high current 20mA LEDs.