Minecraft 1.18.2, mod version tis3d-1.18.2-forge-1.6.8+2ac5c5f.jar
Manual says that you can write ROM module by using it on a RAM module. I've tried this to no avail - ROM always retains its state regardless of what I try to do.

Okay, there's one thing that I didn't notice before: this only happens when you've got something placed in offhand slot. The ROM editing slot pops up instead of contents of RAM being transferred to ROM. Also the manual should say that you have to hold shift down for the transfer to work (this wasn't obvious at first, realized it after looking at the source code).