Just another question:

The 16877 uses the voltage supply as its reference voltage by default. Meaning that by default,

VREF- = 0V
VREF+ = 5V

How do i change the reference voltages? Is there a way where i can do it directly by just programming the PIC? Or do i need an external connection?

For example,change to

VREF- = 2.5
VREF+ = 4V

THanks.