Direct TDM connection with SampleCell II / SampleCell II Plus is not possible on Pro Tools|HD systems. You can still install SampleCell II / SampleCell II Plus cards in Pro Tools|HD systems, but you will need to use the analog outs of the SampleCell cards. If you intend to use SampleCell cards with your Pro Tools|HD system, you will also need to install the DigiSystem INIT that was included on your Pro Tools|HD installer CD.