I believe what you say is correct, however I didn't want to 'bet the farm' on that so decided to reset back to the conditions before the function call. If you want 0, that is fine with me, although I'd like a 'const uint32_t' which is used to symbolically unset the value so we follow our conventions of 'no magic numbers'.
What I'd like to see is this code properly reset itself even after an exception.