I found another datasheet that does describe the protocol used by this chip. While the specifics for a "1", "0", and "F" differ from Holtek, the overall approach is very similar to the HT640. A bit period depends on the encoder oscillator frequency (set by an external resistor) you still need to capture some codes to determine the bit period. And there are some encoder pins that can be used either in the address or in the data so you'll need to determine that, also. Then you should be able to adapt Bruce's HT640 code to work with the PT2260.