Stupid-amaranth-soc-QuestionMondays: 

So I was fooling around with the new amaranth-soc csr registers over the weekend and noticed something that I can't figure out if it's weird or not…

So when you have a register with a bunch of fields and you write to one of the fields it will trigger w_stb on all the fields in that register…

At first I thought it was because they're all part of the same byte from the software side so I put in some padding to byte-align the fields but it still happened.

Then I thought maybe that svd2rust is a bit eager to do u32 writes, so I tested it with a raw pointer doing u8 writes which -- weirdly -- still showed me the data in w_data but then w_stb was no longer being triggered on any of the fields including the target field.

I could wrap my head around the csr bridge simply triggering w_stb on everything irrespective of the field being written to but then, as a total n00b, I really would have expected the w_stb signal to be attached to the Register itself rather than the fields… 🤔 

Is this a bug or just normal behavior?