Under rule 306a.4 of the rules of civil procedure, the trial court's plenary power to grant a new trial is extended when a party adversely affected by the judgment or his attorney fails to receive notice or actual knowledge of the judgment within twenty days after the judgment is signed. TEX. R. CIV. P. 306a.4; see TEX. R. APP. P. 4.2. In order to invoke the protection of rule 306a, "the party adversely affected is required to prove in the trial court, on sworn motion and notice, the date on which the party or his attorney first either received a notice of the judgment or acquired actual knowledge of the signing and that this date was more than twenty days after the judgment was signed." TEX. R. CIV. P. 306a.5. Rule 306a places the burden of establishing its applicability on the party seeking the extension; only when the sworn motion makes a prima facie showing of lack of notice is the trial judge required to hold an evidentiary hearing. In re Ray, 967 S.W.2d 951, 953 (Tex. App.-Dallas 1998, orig. proceeding). After hearing the motion, the trial judge "must sign a written order that finds the date when the party or the party's attorney first either received notice or acquired actual knowledge that the judgment or order was signed." TEX. R. APP. P. 4.2(c).