The defendant challenges the trial court’s retention of jurisdiction over the first one-third of the sentences imposed after he pled guilty to charges of kidnapping and aggravated battery. Section 947.16, Florida Statutes (1981). Since the record shows that McIntyre neither objected to this aspect of the sentence nor sought to withdraw the plea on that ground below, the point— which essentially concerns the voluntariness and knowledgeability of the plea, Viars v. State, 415 So.2d 75 (Fla. 1st DCA 1982)— may not be raised on this direct appeal. Robinson v. State, 373 So.2d 898 (Fla. 1979); Ratushinak v. State, 425 So.2d 1204 (Fla. 3d DCA 1983); Medina v. State, 411 So.2d 323 (Fla. 5th DCA 1982); Griffin v. State, 403 So.2d 623 (Fla. 5th DCA 1981). The judgment and sentences are therefore affirmed without prejudice to the filing of an appropriate motion under Fla.R.Crim.P. 3.850. Ratushinak v. State, supra; Griffin v. State, supra.