If you have a template to convert from A&H to HUI and back again, you should not need anything else. MCU is different than HUI and Pro Tools will not support that.
Yes, as an emulated HUI device, ProTools is looking for a ping response for every ping it sends. 90 00 7F is the raw ping message and the controller would respond with 90 00 00.
There are various HUI templates on or forum you could start with. You might start here.
Steve Caldwell
Bome Customer Care
Also available for paid consulting services: bome@sniz.biz