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Analog input noisy when timer is 8Khz - ADuC831

I have an application where an ADuC831 is being used to sample a frequency input on Pin 1 (T2) input, and the rest of ADC pins are being used to sample analog voltages.

I noticed that when the timer input is exactly 8Khz, the remaining analog inputs become substantially noisier. Going up or down as little as 30Hz seems to quiet the analog inputs back to normal levels.

Is there something in the internal MUX or converters afterwards that would be susceptible to 8KHz? I've tried changing the order in which my inputs are read and adding settling delays with no change in results.