Effects Hxy and Ixy
From Famitracker Wiki
Hxy and Ixy are the two effects that control hardware sweep up and down, respectively. They can be used only on 2A03 square channels. x = period (0 - 7), y = shift (1 - 7).
The Hxy and Ixy effects can be used for a specific purpose that is beyond their intended use. Because FamiTracker resets the pulse wave's phase when triggering a hardware sweep, inputting H00 or I00 acts as a "phase reset" effect (inserts a "click" in the pulse), which is useful for separating two subsequent identical notes without using note cuts or changing the channel's volume.