When an XMP (embedded processor) source is added to an ISE project, Project Navigator sets intstyle=ise to specify to XPS that this project has been instantiated in Project Navigator. When this setting is used, XPS does not allow certain fields to be modified to allow correct integration. However, if you delete the XMP source from the ISE project, the intstyle value is not reset to default and user control is not restored for the options controlled by the intstyle=ise setting.
To revert back to an EDK-only project, manually edit the system.xmp file with a text editor and change "IntStyle: ise" to "IntStyle: default" and change "UseProjNav: 1" to "UseProjNav: 0"
To allow the simulator to be invoked from XPS, make the modifications below.
1) Select the 'Implement Design in ISE' box
2) Unselect the "Processor Design as a sub-module" box.
3) Select "Implement Design in XPS" box.
This problem has been fixed in the latest 9.1i Service Pack available at:
The first service pack containing the fix is 9.1i Service Pack 1.
With the fix, Project Navigator will also undo the change and make intstyle=default when an XMP file is removed from the project.