Does writing to part of a write register work sanely?

[alexrp]

E.g. if I write to only the upper part of FSTATUS via memory, will this do the sane thing (write to the upper part of STATUS)? Is this the case for all registers that work like this, such as ILATCL, ILATST, etc?

[aolofsson]

All memory mapped registers are 32 bit registers. Trying to do byte/short writes to these memory locations is not supported so there is no way to write to part of a register.

[alexrp]

Glad to hear that! This simplifies things a lot for me.

Presumably, attempting to do byte/half/double-sized loads and stores from/to these addresses is just undefined behavior?

[aolofsson]

Correct.

[ysapir]

Writing/reading to/from MMRs should only be done using MOVTS/MOVFS instructions. These are 32-bit accesses by definition.