Re: MVIO not on PIC
PIC32 devices, and AFIK. also PIC24 and dsPIC33 devices typically have a number of pins that are:
'5 V tolerant'.
This is limited to pins that Not able to be used for Analog input or output signals.
There is no separate power supply for this, but there is some kind of zener structure inside the chip.
The PIC cannot drive a output pin to a higher voltage than it's power supply,
but if you configure a set of Digital only pins with Open drain control enabled,
and arrange external pull-up, there may be output signals with higher voltage than Vdd.
There are limitations. Read the Datasheet,
especially the chapter on Electrical Specifications, and Absolute Maximum Ratings!
8-bit PIC devices are usually Not allowed to be connected to any signal voltage higher than their actual power supply voltage +0.3 Volt,
but see datasheet for PIC18F66K80 family of devices.