If you are curious about reading more, CCSDS is an overloaded term in the space industry for an onion of different OSI layers that are changing all the time. My guess is that the telemetry coding standard CCSDS 101.0-B-6 is likely to have been used on New Horizons. Even though it is now a "historical document", some new space missions still use it.

Here is a copy: http://public.ccsds.org/publications/archive/101x0b6s.pdf