Why RTL ATPG?

Register Transfer Level(RTL)Automatic Test Pattern Generation(ATPG) has been of wide conceran for two decades .Meanwhile gate-level ATPG has made remarkable progress in dealing with large circuits.An argument is then posed.Do we need RTL ATPG in the case of gate-level ATPG capable of generating tests for large circuits? This paper attempts to answer this question .The necessity,difficulty,and major interests of RTL ATPG are reviewed.