It would make way more sense to purchase a much more modern debugging setup such as that from SiLabs and do the work to test and debug product changes with that. That will cost you at most a hundred dollars or so. Then when you get the changes worked out you can re-target the code back to the original type of MCU (or look at replacing it with a FLASH based part). I have a writeup described at this link where I did this very thing.

If the product that you are working on has enough going for it that makes it justifiable to even think about writing an IDE for an old ICE box then maybe it would actually make far more sense to spin the boards and apply a new chip family that has onboard JTAG type debugging capability.

Also please consider that the Keil uVision IDE and 8051 development setup has a facility where there is a DEBUGGER interface API built in. Using this it is possible to supply a DLL that can link a set of debug hardware up to the Keil environment. It would be far easier to build this DLL and interface the old MICE11 system to the API in the Keil IDE than it would be to write a whole new IDE. I would use one of my former suggestions but the DLL is a distinct possibility. There is information about this API at the Keil web site.

Michael Karas