Overthinking what must be simple

[mackrackit]

No, wait a minute. Adding won't do it, will it? 01111111 + 01111111 = 11111110

Hmm....

Yep,
127 + 127 = 254
As long as you only use seven bits on each port and add those you will stay below the 255 limit.

How many combos can you come up with using two 7 bit numbers like that. One heck of a comination lock.