MOV function to TON Accumulator

I have a program that runs a CPM Pelletizer. It has shear pins that break when rocks or other debris lodge in between the rollers and die. When the shear pins break the shaft spins freely and cams trigger a limit switch.

The limit switch is a XIC in the program that starts a timer. The timer .DN latches in a Shear Pin break alarm. The problem is the limit switch makes and breaks each time the shaft rotates 90 degrees. The Preset was initially 1000ms, I moved it to 5 ms. Is there a better way to solve this problem?

I noticed that other timers in the program have an MOV function that writes to 1000ms to the Accumulator and the Preset is set to 1000ms. Does this make the .DN true each time the rung is true?

Its a pretty big program and it is very easy to run into the unintended consequences, so I like to make as minor programming changes as possible and triple check everything.

If it were me, I would get away from the timer altogether and use a counter instead. If you really want to stick with the timer then I would use a retentive timer (RTO).

What is the timer measuring?