to make a car ther is no need of microcontril
you connect D0,D1,D2,D3pins of ht12d
decoder to L293d motor driver
her all pins are by default HIGH
to move forward or backward you need to press
two switches simultaniously
i tried it and its working
use the circuit in EGLABS
connect d0,d1,d2,d3 to L293Dmotor driver
instd of leds
use this
http://www.engineersgarage.com/electronic-circuits/wireless-rf-remote-control-circuit