Chuck(G)
25k Member
Slightly OT: The NSC800 (Z80 CPU in 8085 clothes) did have an interesting quirk. The ICR lis a write-only register lying at I/O address 0xbb. However, it can only be written to by instructions "OUT (C),A" and "OUT (N),A". Block I/O writes are unaffected. So, in effect, you have an I/O space of 256½ ports.