On 23 July 1914, the Austro-Hungarian Minister of Foreign Affairs Leopold Count Berchtold (pictured) sent a private coded telegram to the Austro-Hungarian Ambassador to Serbia Baron Wladimir Giesl. In his telegram, Berchtold informs Giesl on the procedure to follow when he is to deliver the Austro-Hungarian ultimatum to Serbia.
Count Berchtold to Baron von Giesl in Belgrade. Vienna, 23 July 1914.
We learn that [the Serbian Prime Minister] Herr [Nikola] Pasic intends to render his resignation at the moment of the presentation of the note. The resignation of the cabinet would change nothing in our demands nor in the duration of the term for the answer, since a resigning cabinet always carries on the affairs of state until a new ministry has been named, and is fully responsible.
This is for your information and the direction of your audience with Pasic.
Source: 1919 Austro-Hungarian Red Book, with minor edits.