Tool/software: Code Composer Studio
I am testing a circuit for EMC between 80MHz-230MHz frequencies. I face a problem on analog inputs A3 and A4. Under test, I read high analog values. For understanding the reason easily, all analog inputs were seperated from circuits connected. When apply frequencies, I am seeing abnormal voltages on A3 and A4 again. However, other analog inputs stay in normal state. That means only A3 and A4 have different behaviours from others.
In MSP430x2xx Family User's Guide, Figure 22-1. ADC10 Block Diagram shows that A3 and A4 are connected to referance voltage part. I guess, the problem is starting from here. I configured some registers as below. However, I cannot resolve the problem.
ADC10CTL0: SREFx is '000' (VR+ = VCC and VR- = VSS)
ADC10CTL0: REFOUT is 0 (Reference output off)
AC10CTL0: REFON is 0 (Reference off)
Do you have any suggestions ?