In a few idle moments (well waiting for tests to finish running) I was reading up on the 680x0 bus in the 68030 User's Manual. I've read the description of the Function Code (FC) pins several times now, and I cannot imagine what a peripheral is meant to do with them. It's great that they indicate whether the computer thinks it's pointing at User or Supervisor space and Data or Program space, but in the end, it's still all the same 32 bits of address space.

So, anyone know if there's some reason why a peripheral for the SE/30 actually needs to decode the FC pins, or can it safely ignore them?

If a read or a write to a particular address shows up on the bus, and that address is within the peripheral's address space, what affect would the FC signals have on how the peripheral processes it?