Re: [Simulavr-devel] SBI vs. PINx and interrupt flag registers

[panic]

Michael Hennebry:
> I suspect the practical thing to do is
> give each IO register an sbi and cbi method.
> They could all be implemented as a simple read-modify-store,
> a store or a complicated read-modify-store.
> Note that "read" means just get the value in the register,
> do not produce any of the side-effects, if any, associated with a load.
> "Store" means store, as in STS or OUT.

It is not the "store" that is the problem -- it's the "read". Normal
read of a PINx register returns the state of the input stages. However,
"read" during SBI instruction returns 0x00, always.