Hi Phil, Thank you for your detailed post. This behavior seems strange, especially since you seem to be within the recommended operating temperature (-40C to 85C). Could the part be reaching 85C somehow? Could you try testing this with the MSP430G2253 isolated from all other inputs and outputs (except supply power obviously) to rule out external influences? However, this could be an oscillator fault. Since you are using the internal calibrated oscillator, keep in mind that the DCO will change frequency with temperature changes. Since the MSP430G2253 has an internal temperature sensor (not very accurate, used for monitoring the junction temperature), you could change the values of the DCO control registers to keep the DCO frequency in the proper range. This would require calibrated lookup tables covering the expected temperature ranges. Take a look at page 30 in the datasheet for the Calibrated DCO Frequencies and Section 5.2.5.2 Adjusting the DCO Frequency in the User's Guide . Regards, James MSP Customer Applications
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