Normally one writes 0 to an event register to reset it.
I am writing a uart driver and when I open my interface I want to prime my transmit pump by setting EVENT_ENDTX to 1 so that if I enable it's interrupt mask, an interrupt will occur and in the irq service routine I can pull data from my ring buffer to send it via easy dma.
Without that capability i am having to send my first packet after opening in my background task and then the tx pump keeps going.
Look forward to hearing from you