hello
in the datasheet , explanation is Serial data , so the ID tag of RFID can be received by using UART 9600,8,N,1
we can suppose 8 bits, no parity, one stop ...
and you will receive 2 bytes (minimum)
i don't know if it is raw data or a via a special protocol used by the emitter part ?
MSB + LSB -> 1 Word 16 bits
or maybe LSB + MSB ... motorola fashion or Intel fashion
If you now the ID reference on the Emitter , you will able to recognise the 2 bytes .
you better have to use interrupt traitment for receiving data, if data flow is continuous.
(no time gap beetween invoice by emitter)