Hi Sara, For your external crystal oscillator, the manufacturer should specify a certain load capacitance (e.g. 12 pF). As you mentioned, the XCAP bits of the UCSCTL6 register configure the internal load capacitance. The values found in the User's Guide are most likely for a slightly different device - it's always best to trust the datasheet over the User's Guide for a specific device. I'd recommend reading through the MSP430 32-kHz Crystal Oscillators app note. Specifically, take a look at Section 2.1 Effective Load Capacitance, which discusses sources of parasitic capacitance including the pin capacitance of the microcontroller and PCB traces. There is a load capacitance equation and example of picking the proper load capacitance as well. In the "msp430x54xA_UCS_6.c" code example (mentioned in this thread already), you can change the internal load capacitance changing XCAP_x field for UCSCTL6 register. UCSCTL6 |= XCAP_3; // Internal load cap In the header file for the MSP430F5438A , there are four XCAP defines that corresponds to 1, 5.5, 8.5, and 12 pF in the datasheet. After calculating the effective load capacitance, use the appropriate XCAP define. Regards, James MSP Customer Applications
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