Finally the debug effort is finished. I traced the no boot issue to a bug in ProDOS. This error exists in both ProDOS version 1.2 and 1.9. But I see it has been fixed in version 2.0.1. I just need to do a work around in my ROM code to make sure I do not trigger this bug. Then I can continue firmware development of the Serial Virtual Drive. When I get this working, the floppy is the next task. I have done some testing on the floppy and I believe it is working. But the final test will be to load a DOS 3.3 image into the RAM and try to boot from the floppy.
These are not great quality, I took them with a camera phone. I wanted to show the status of the project. Not much has changed. As long as I have only the one drive, everything works correctly. But when I add a second drive, either floppy or serial drive, ProDOS fails to boot. I am again tracing ProDOS boot sequences to see where it fails. I do not know what else to do.