Shevarim - Terua בנשימה אחת?(Erchin 10a)

The Rishonim have a major מחלוקת how you blow it, בנשימה אחת or שתי נשימות?
The Machlokes is based on a Gemara in Succah(53b) and our Gemara. The Gemara discusses the תקיעות in the מקדש. R' Yehuda holds that תקיעה תרועה תקיעה is 1 מצוה and therefore אין בין תקיעה לתרועה ולא כלום.

The Ritva, Ramban and others learn as follows. They read the Gemara literally that according to R' Yehuda there is absolutely no הפסק between the 3 קולות because they are 1 mitzva. Therefore they say even though we don't paskin like R' Yehuda, his din applies to שברים תרועה. Everyone agrees that שברים תרועה is 1 mitzva and therefore you cannot be מפסיק and שברים תרועה is בנשימה אחת.

Rashi and Tosafos in Succah learn that אין בין תקיעה לתרועה ולא כלום means you can't be מפסיק more then a נשימה. However, since these are separate קולות you are מפסיק a נשימה between them, which means that they hold שברים תרועה is בשתי נשימות.

There also is a מחלוקת what does בנשימה אחת and שתי נשימות mean. The Mishna Berura writes that נשימה אחת is if you were מפסיק less then a נשימה. The חזו"א disagrees and says that נשימה אחת is no הפסק whatsoever (and this is what the Rishonim seem to say). By שתי נשימות you have a similar dispute. The חזו"א holds that it means a הפסק but not an actual breath and may others (Shulchan Aruch Harav, מקראי קדש, etc.) hold you should specifically take a breath.