7408 AND Gate, Odd Behaviour
You do not need the NOR gate to detect low on either UDS or LDS or both. The 7408 AND gate can do that in a single gate. 

UDS LDS  OUTPUT
 L   L     L
 L   H     L
 H   L     L
 H   H     H


As you can see you can get a low out of the 7408 when either LDS or UDS are low.