UART RFID SL025M

hi all

i have bought an RFID (SL025M) ,and connected it withh my Arduino throught pins 0and 1 ,uploaded this sketch after downloading its library

it can work without modifications on 0022 version

but the problem now is printing infinite 01010101... when there is no card to be read
the data sheet can be found here
http://www.stronglink-rfid.com/download/SL025M-User-Manual.pdf

thanks in advance

any help?