Hi, the HT12E and D are not really made for this form of data transmission however try the following, try using synchronous data by using the /TE input. This should restart the transmit data process to use the new data of the D8-D11 pins.
ie
TE _____/-----\_____/-----\_____/-----\_____/-----\_____
D8 _______/-----\_______________/-----\___________ to D11
D8 input = D8 output = 101
Data is valid on the the falling edge of /TE
Alternatively, only clock the /TE input when data on the inputs changes rather than use a continuous clock.
Hope that helps Greg