A custom region is a type of location assignment. You can define any arbitrary rectangular region of physical resources on the target device as a custom region. Assigning nodes or entities to a custom region directs the Compiler place those nodes or entities inside the region during fitting.
A custom region exists in a project only as long as there are nodes or entities assigned to it. If no nodes or entities are assigned to a custom region, information about the region is not saved when you close the project.
You can create custom regions for supported device (MAX II) families.