ht 640 decoder

we are doing a project on wireless message communicator using ATMEGA8515....we were able to interface lcd and keypad....we are using Holtek encoder HT640 and 648L decoder along with tws434a transmitter and RWS434.....but first we thought we would give some data to the encoder manually and connecting led's at the decoder end to test whether encoding and decoding process is going fine...but we are not getting the output..we tried doing the same thing using the transmitter and receiver...but to no avail..so if anyone of u have worked with these things...plz guide