I did just what you are proposing to do. I went one further and used a Cygnal part and the debugger in the IDE to debug the code and then re-targeted to the off-Cygnal part in the application.

See...
http://www.8052.com/users/mkaras/Cygnal_ICD.phtml

I installed a command batch file on the IDE Tools/Add-Remove User Tool to run the OH51 utility to convert the OMF object file to HEX format.

If you want to automate this process you can instead go to the Project/Target Build Configuration dialog and switch the build process from the internal mode to Execute Batch File mode. Then you just need to make a batch file to perform the compile/assemble/link steps and add in the OH51 conversion at the end of the batch file. If your project has multiple sources then using the batch file approach may want to implement a make utility so that you do not need to recompile and/or re-assemble all source files every time you launch a build.

As an interesting note.....the earlier Cygnal IDE implementations did not have a smart build when the internal build mode was used. As such they would recompile every source at each build launch. If you have an IDE from the version 1.7x or earler you should go to their web site and download version 1.85 which now includes a smart project build capability.

Michael Karas