For the investigation of the latch logic issue for the CARM CM board, I have made the LED logic checkers with DB breakout boards. They require the pull up voltage supply of +15V because the acromag digital out is a open corrector (well... open "source") output.
The logic from Pin1 to Pin16 of DB37 can be monitored. The DB15 connector is only for monitoring the latch enable logic.
What Gautam and I found with the logic outputs was that the latch logic works fine but occasionally we found that the top 2 bits and the bottom 4bit were processed independently.