OK, so here's the terminal connection:
Seems you just need to open up the correct family utility (ignoring all error messages since there's no SATA drive connected). Make sure to select "ATA/COM" as the access method. Open up a terminal window and press enter to verify that you get the ">" response. Then you can just do Tests > Service Information > Work with service area > Read ROM (Terminal).
It's very slow reading as jol pointed out. Also there is the limitation that you can only read it, not write it through the terminal. At least not in the version of PC-3000 I have. I suppose you could try to manually extract the CP's from it, or use a programmer to write it to a new ROM chip. Basically I can't see any real use for it other than to just backup the ROM before physical transplant. Just in case you cook the chip and need to be able to rebuild it in a pinch.
Now that I'm looking at it, I think I did do this before but discounted it after I realized you couldn't write the ROM back this way.