How to make a famicom cartridge rom dump device?

[byemu]

can you release a custom rom,
can :
1 specify address to write data！
2 specify read address range to read vrom via audio.
3 specify read address range to read prom via audio.

It's an idea that I might work on someday... but I still have many things on my plate right now (including a baby...)
For now, you're better off modifying an existing mapper definition (there is a program that assembles them included in the source code directory.)

Thanks and good luck!