We’ve stated that dsPIC33 devices are not drop in replacements for their dsPIC30 counterparts, and while that is technically true, in reality all but one pin are exactly pin compatible. That one pin is associated with the new regulator function on the dsPIC33 devices and provides a location to attach an external capacitor to filter the regulator. It replaces a ground pin of the dsPIC30 devices. It is very easy to design a printed circuit board in which either a capacitor to ground or a jumper to ground is connected to this pin providing a board which can use either family of devices.