assumes DW-CAS is the VS CSRs 00 01 XXXX 0x100-0x1FF Standard read/write 01 10 11 10XX 0xF80-0xFBF Standard read-only 11 01 10XX 0x580-0x5BF Standard read/write 10 10 11XX 0xAC0-0xAFF Custom read/write