I tried that (mixing old 8 bit into a 16 bitter capable of running it

fuggetabut it

You end up modifying all to 16 bit (even with a 251)

Is this commentary based on experience with the 251 or is it based on another architecture that you feel is like a 251?

For what it's worth, in binary mode, the 251 IS an 8051. It's 100% compatible with the OBJ files. In fact, you can actually hook-up an existing 8051 ROM to the 251 and it will run just fine.

If you want to convert the original 8051 code to 251 code, you can simply compile it with the 251 compiler, at least that's what you can do with the Keil tools--I think other tools work similarly.

I have done this with a large number of 8051 applications that we converted to 251. For binary mode compatibility, I didn't modify any of the OBJ files (except for the startup code--but even that was not required). For source mode compatibility, all that was required was a simple re-compile with the 251 compiler. Each of these requires only a few minutes.

Jon