Сhoose source port or destination port, jumper configuration will be updated automatically. You can also click on jumper to toggle its state.
"INV" means address bit is inverted, "PASS THRU" means bit is passed through as-is.
The "source/target" ports represent a logical mapping: we're remapping the board's port to a different address, but electrically it's the reverse - we're selectively inverting address lines (A7-A4) controlled by the Zeal 8-bit computer to make the board think it's working with the same port as before.