It doesn't actually have to be in code; it could be in ROM (or a section of a ROM) that appears in XDATA.

Keil provides facilities to do this - search the Keil site (including their discussion forum) for "XCONST."

As I haven't mentioned the Triscend E5 for ages now, I will just take this opportunity to say that this is an absolute doddle on the E5 - because the mapping of the 32-bit external address space onto the 8032's CODE and XDATA spaces is all fully configurable at runtime via the Mapper registers...!

PS
Other than as a user of their products, I have no affiliation to either Keil or Triscend.

Andy Neil,
Antronics Ltd.