I've looking at this with a view to seeing if the function is causing timing oscillations in my car.
Being Volvo the function is a little different, but does follow the FR, although tans is in there too.
This is what I'm seeing in my logs, not sure if it's ARMD or not at this stage.
From looking at the FR and code it looks like if dmar_w > 0 then it will set the b_ar bit.
I'll have to do some logging to verify.