Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Formula
FORMULAFIELD_STRINGParameter: t,d - Time, Delta Time
FORMULAFIELD_TIMEParameter: f - Frequency
FORMULAFIELD_FREQParameter: Subfields
FORMULAFIELD_FIELDS