Modulus and Non-Negative Finite Field

Hello all,

I noticed that when I set a modulus in the HP, say 8, it uses the field (-3, -2, -1, 0, 1, 2, 3, 4). How do I get it to instead use the field (0, 1, 2, 3, 4, 5, 7) for its calculations? For addition and subtract, I can just internally shift, but what about things like inverse mod?

Thanks,

Titus
.