Impedance Matching Resistor
There are matching series resistors connected between output digital
  pins &amp; controller


In these circumstances (fast digital signals crossing a significant distance on a PCB) you choose matching resistors to suit the impedance of the copper interconnection. The copper interconnection, just like coax cable or twisted pair cable exhibits characteristics that if not properly matched, can cause reflections when the fast edges of the signal reach the receiving device. This will inevitably lead to data corruptions.

On the other hand, if the tracks are not too long (compared to the wavelength of the fastest parts of the signal), maybe the resistors are just pull-ups. There are decent rules of thumb that govern the need to apply terminations of course.

If you need a more definitive answer, a section of the circuit would help as well as a picture of the copper tracks on the circuit board.