How do I modify a custom system TLC to generate AUTOSAR C-code and ARXML files?

I have a custom system level TLC file that I need to modify to generate AUTOSAR compliant C-code and ARXML files. Both the autosar.tlc and my custom.tlc files are derived from ert.tlc.

So far, I've tried making custom.tlc derived from autosar.tlc. I've also tried making autosar.tlc derived from custom.tlc. Both were unsuccessful, so it looks like the solution will probably be to make a new file consisting of lines from both custom.tlc and autosar.tlc.

There doesn't seem to be very much documentation on modifying TLC files. It would be very helpful to know which lines from autosar.tlc are necessary for generating AUTOSAR code and the ARXML files. Any documentation or suggestions would be appreciated.

Thanks,