< I can't imagine any sensible reason for making them default to edge-sens < the 8259 is very flexible and can be configured either way. I can only < surmise that they had no clue and decided by flipping coins or throwing < darts. Sounds about right. Sharing can be done but the drivers have to have a local pull down and be logically open collector(or emitter). Of course you can reprogram the 8259a too. Allison