If you have the Ultimate mapping resource pack from A boojam snark press
then on the right under Catagories, choose the doors prefab and select a setupgate door. Change the Select option on the top right to "objects" and disable props in the visgroups tab, then rename each of the doors (example Onewaydoor_top for the top door and Onewaydoor_bottom for the bottom door) and go into the outputs for each door and delete the "On fully open, Kill" output. Then using
use the trigger texture as you would a regular door and make it a Trigger_multiple entity, then put in the regular outputs for a door, just instead of listing each door's name, list it as "Onewaydoor_*
" the * at the end targets all entities with that name. then just move the trigger to one side to allow only that side to open the door. I can provide images if you do not understand what I am saying.