data scrambler block implementation in simulink

hi , i am designing a data scrambler block in simulink. it is for wimax system so i have designed one using delay units, XOR gates.i used the specification specified for the initial condition of delay elements and feedback connection according to wimax forum specifications, but i am not able to generate randomized output.im not sure if somethings wrong with the sample time or data type and that is why it is not generating proper random output. i have attached simulink model below. thank you very much.