Trellis Coded Modulation（TCM） has been widely used because it can obtain 2. 55 ～ 7. 37 dB coding gain without bandwidth expansion or reduction of the effective information rates. Since Viterbi Decoder（VD） plays an important role in the realization of HDTV system

we conduct the research and development on integration of VDs. This paper studies the factors which affect the performance of VDs and their solutions. A completed VLSl circuit design for an 8-state 32QAM VD（30

000 gates in scale） is also reported.