In reply to Jonathan_Alvarez:
The whole ‘busy’ mechanism is busted. The register model is poorly architected in this respect, because for some reason the developers decided to mix prediction with stimulus creation (accessing the registers).
Instead of rolling your own quirky register, you can just call ‘Xset_busyX(0)’ on the field before predicting it. It’s a “hidden” function, in that it’s not part of the standard, but it’s a more pragmatic approach.