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Altera_Forum
Honored Contributor
21 years agoYes, most on-chip ROMs are writable when the processor is in debug mode.
To explain - when Quartus instantiates a ROM it's normally using M4K blocks but not connecting the write enable. SOPC builder ROMs have the write enable connected, but gated by a signal which the processor outputs when in debug mode. This is safe, as when the processor is in debug mode its running a debug monitor supplied by nios2-gdb-server. This monitor can be used to write code into the ROMs if you change it from within the IDE to save you from having to download a new SOF. Next time you synthesise the design Quartus will pick up the most recent output from the IDE and put that into your SOF file.