Yes, but it's a hack. Standard issue '51/'52 architecture separates the memories - MOVX is for R/W on data, MOVC for Read on code - or at least that's what the original designer intention was - and anything that allows MOVX to access code memory (or any code memory write operation for that matter) is beyond the basic specs and is some proprietary extension, either of the microcontroller manufacturer or your (circuit designer's) own.

By default (and recommended for beginners) the above point doesn't exist - no accessing code memory by MOVX, neither for read nor for write. Reading with MOVC or at standard code execution only.


Or RAM (obviously).