Create a special chip, often called a bond-out chip. You replaced your microprocessor with the expensive bond-out chip and connected it to your very expensive in-circuit emulator. In fact, the history of the 8051 notes that they developed the bond-out chip first. For example, the Lauterbach ICE-68300 here could take a bond-out chip or a regular chip, although it would be missing features if you didn’t have the special chip. In any event, on chip debugging or real in-circuit emulation, it sure makes life easier.