You could consider using the SiLabs downloadable FLASH Programming Utilities Kit and roll your own custom programming shell around the access DLLs provided. Using this you could "see" the chip type and then dynamically modify the programming image on the PC before downloading the image to the target MCU.

While not the same type of application I have done similar things in the past where I embed an eye-ball string into the source code that ends up in the target object image. Such string in this case could be "Target MCU Type=xx" where xx is the variable parameter. The dynamic utility that you could create would get the processor type from the SiLabs DLLs and then search through the programming image for "Target MCU Type=" and then plug in the appropriate xx value for the MCU.

This scheme would take some one time work but saves the extra cost and or labor to deal with an external marker EEPROM such as Erik suggested. Of course if your product already has a serial EEPROM you could deploy a location or two in it for the marker tag.

If you are using your own bootstrap loader scheme to allow the MCU update via COMM port, USB port or other such interfaces you could choose to craft the boot loader to be agnostic to processor type in the actual code and then use the host side user interface program to "tell" the target MCU what type it was which in turn the boot loader itself could program into a reserved FLASH area.

Michael Karas