Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Councils of Ancyra, Gangra, Neocæsarea, Antioch and Laodicea, which Canons were Accepted and Received by the Ecumenical Synods.: Canon IV

Canon IV.

Concerning those who have been forced to sacrifice, and who, in addition, have partaken of feasts in honour of the idols; as many as were haled away, but afterwards went up with a cheerful countenance, and wore their costliest apparel, and partook with indifference of the feast provided; it is decreed that all such be hearers for one year, and prostrators for three years, and that they communicate in prayers only for two years, and then return to full communion.

p. 65 Notes.

Ancient Epitome of Canon IV.

Such as have been led away and have with joy gone up and eaten are to be in subjection for six years.

In the Greek the word for “full communion” is τὸ τέλειον (“the perfection”), an expression frequently used by early writers to denote the Holy Communion.  Vide Suicer, Thesaurus ad h. v.

Bingham.

[The Holy Communion was so called as being] that sacred mystery which unites us to Christ, and gives us the most consummate perfection that we are capable of in this world.