At p&r, rom and ram connect to digital power ring, and i think rom , ram is analog , Does rom, ram need to connect to analog power ring. And analog modul direct connect to pad through special net by hand,don't need analog power ring.
If you have a complex design and it generates a lot of noise you can put the memory in a different power ring.
If your design have an analog block and a memory block is high recommend to isolate the analog from the rest of the circuit (it means the memories can be with the logic power source).
When using different power ring, normaly is to isolate analog signal from noise creating by digital signal. So just let analog part with a ring, others (include ROM, RAM) in a another ring.
Of course, in complex application (high noise), can take memory part in a ring.
hi chuchinh, i think that analog power don't need power ring, just direct connet macro power to analog power pad, I think this will have little noise, does it?