PICDEM™ 2 Plus Demonstration Board: Oscillator Assignment
The PICDEM™ 2 Plus Demonstration Board (DM163022a) has two MCU sockets: a 28-pin socket and a 40-pin socket. Pins 9 and 10 of the 28-pin socket are connected to the OSC pins (13 and 14) of the 40-pin socket. (This connection is not described in the schematic but can be tested with an ohm-meter.)
These connections allow you to have a crystal connected across pins 9 and 10 driving the 28-pin part from Y1.