MSP430FR6989: How will the MCU deal with the internal negative variables before send it to the output pin or if it is >3.3 V

Part Number:MSP430FR6989

Hi,

I'm connecting a polymer device with the MCU, at first I do some calculations in the MCU based on a certain algorithm, the result of these calculation Vout goes as an output from MCU to the polymer device, then there is a feedback from the device to the MCU  Vin, here I have two questions :

1- In the first step Vout could be > 3.3 V and I know the MCU Vmax is less than that, how can I solve this issue?

2-If Vout in the calculations is negative,how will the MCU deal with the internal negative variables before send it to the output pin?

Thanks