The Event Viewer’s PPU view allows you to visually check the timing at which various events (register read/writes, NMIs, IRQs, etc.) occur. This can be useful when trying to perform timing-critical mid-frame changes to the PPU, or to verify that PPU updates finish before vertical blank ends, etc.
The colors can be configured and it’s also possible to define breakpoints as marks to be shown on the Event Viewer. This is done by enabling a breakpoint’s
Mark on Event Viewer option. This allows the event viewer to be used to display virtually any special event that needs to be tracked.
Show previous frame's events option is enabled, all events for the last full frame (e.g the last 261 scanlines for NTSC) will be shown. Otherwise, only events that have occurred since the last pre-render scanline (scanline -1) will be shown.
The list view displays the same general information as the PPU view, but in a sortable list.