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Which version do you have? The datasheet lists a 48 pin DIP and 52 pin PLCC. In either case, Eagle has the chip outline ("package"). That is the hard part of making an new device. Look in smd-ipc.lbr and smd-special.lbr. If it is the DIP version, you might look in Microchip and find something similar where you will only need to modify the pin names.