John,
A rigblaster is an interface only, but can be used with the correct software as a TNC for most digital modes. I use MixW which emulates a basic TNC, including a KISS mode output which works with all the programs I have tried which expect to see a KISS TNC. There is another program, Packet Engine Pro, which works well as long as you only want the basic packet modes. There is also a freeware version.
Note that while MixW will work at 9600 baud, the rigblaster will probably not. The isolation transformers found in all good interfaces will not pass the range of frequencies needed at 9600 baud and up. In principle you could build an interface that would word, but all those who have reported success using MixW or similar at 9600 baud go directly from the sound card to the rig.
Alan WA4SCA