Hi Darrel,

Yes, it helped a lot - thank you.

It is now fully functional and exactly what I want. Certainly was a case of me trying to over-engineer the requirement and overlooking the obvious, no interrupts needed only a check of the appropriate flag, as you diagnosed.

I learnt a few things on the way - bonus! I expect your DT_INTS will now be a large part of my projects in future, I see how they can make things so much more efficient.

Thanks again and best regards,
Bill