Why RTL ATPG?

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