I want to change the DPXL from 01h (default) to FFh(the region address of the code memory) So I can access(R/W) the code memory by the inst(MOVX) When I use the simulator of the C251 eval version, there's error message while I access in this way. the message is "error65: access violation at 0xFF0300: no 'write' permission" Is this a constraint? or I can change some setting to solve this issue. Thans for the great help. :)