HP-87 and HP-9122D

[stephenpeterson]

I can INITIALIZE and use DSDD floppy disks with my HP-87, an HP-9121D disk drive and the PRM-85 ROM Emulator board.
However I cannot Initialize a DSHD floppy on an HP-9122 disk drive. If I type INITIALIZE 15,2 (which I think should be supported by the Extended Mass Storage emulation on the PRM-85 board) I get an ERROR 84 EXCESS CHARS.
This seems like the EMS ROM is not supported although the jumper is in the correct position (16 to 24) on the board.
Now, I don't have 100% confidence in the 9122 yet, but given that, I wouldn't have expected an error 84 immediately without any drive access if that command is supported by the EMS. But I am still re-learning. Any thoughts?

Thanks in advance,
Steve