-- read SID port BFFD
и вот
nsid_addr_s <= not cpu_a(14);
nsid_cs_s <= '1' when ay_select = "00" and enable = '1' and cpu_iorq_n = '0' and cpu_m1_n = '1' and cpu_a(15) = '1' and cpu_a(2 downto 0) = "101" else '0';

все, что известно)