Toshiba HX-F101 external floppy disk drive problem.

Could you dump on the MSX the whole slot of the disk drive? Then we can see whether the ROM and/or the registers are mirrored in the slot.

If you put it in your MSX slot 1:
- saverom fddslot.rom
- Primary slot: 1
- Secondary slot: 0
- Select type: Normal
- Begin address: 0
- End address: ffff

Quick analysis:
HX-F101 has a WD1793 compatible controller at 07FF0H
FDD busy led at 07FF4H (b2) w ?
Drive select at 07FF5H (b0) r/w ?
Disk change at 07FF6H (b0) r/w ?
DRQ/IRQ at 7FF7H (b7,b6) r
Only media with mediabyte 0F8H and 0FAH are readable by diskdriver
drive is single sided

You mean it's wrong with the saverom?.

Yes, thanks a lot! I just shared the conclusion of the analysis.

This device is now emulated in openMSX.
@zeilemaker54: thanks for the annotated disassembly, it was helpful.