Hi Rob Klein !
I am Sorry !, What U say is correct.
I was thinking that there are already 256 opcodes from 0x00h to 0xFFh and take 8 bit data bus and 8 bit memo cell to store .. So adding some more function in the controller will need some more instruction for it .. that means an opcode for it ! so one more bit. So I thought .... some extra instruction is needed. I forgot about the memo mapped concept.
Well, Ya port 5 and 6 will be memory mapped .
regards
Vignesh Baliga