here's another potential "gotcha" pertaining to the words SET and RESET ...
in MOST (but not all) Allen-Bradley documentation, the word SET means "to write a status of ONE into a bit/box" ...
conversely, in MOST (but not all) Allen-Bradley documentation, the word RESET means "to write a status of ZERO into a bit/box" ...
but ...
just to make it confusing, SOME Allen-Bradley documentation will say something like this: "be sure to SET the bit to a ZERO" ...
in all honesty, the ONLY way that I'm personally comfortable with is to ALWAYS refer to the status of the bit/boxes as either "a status of ONE" or "a status of ZERO" ... that way there is never anything ambiguous about the situation at hand ...
now then ...
going a little further into the ONE-SHOT discussion, here's a simple Boot Camp-style experiment that can help understand what's going on under the hood ... (set up the rung in a spare processor, if possible) ...
in the figure below, leave the switch in the ON condition ... then go to the status bit for the OSR and manually toggle it (note that it's so fast that you probably won't see the status change on the screen – but the status DOES change inside the processor's data table) ... watch what happens to the value in the ADD location – and compare those results to the description posted by my distinguished colleague Alaric ... this might help clear up some of the confusion ...
party on ...