flashx20 - Floppy and screen for the Epson HX-20

Fred Cisin cisin at xenosoft.com
Sun Dec 16 21:59:38 CST 2018

On Sun, 16 Dec 2018, Norbert Kehrer via cctalk wrote:
> I have not tested it, but I suppose, that also the PX-8 and PX-4 used the 
> protocol,
> because the protocol specification defines the following device numbers:
> - HX-20: 0x20 (probably also used for the HC-20)
> - PX-8:  0x22
> - PX-4:  0x23

That is especially interesting.

It is probable that the HX-20 worked with the TF20 on a file level load 
and save, but the PX-8 was likely to work on a sector level.

The HC-20s that I had were Japanese machines brought to USA for some 
software develpment in Berkeley.  HudsonSoft?
The HX20 never caught on very well in USA.  It had a few dedicated 
applications, such as CableTV configuration. 
There was no technical documentation available.
I had a little bit of incomplete Japanese documentation.
During the time that I had some machines, the technical manual and 
protocol specification were unavailable in USA.

I don't remember the disk format for the TF20 external drives, and 
they were unavailable in USA.  IIRC, the only sample disk that I had used 
a form of the Microsoft "Stand-Alone BASIC", much closer to the NEC 
variants than the Coco.  (seek center directory, with short directory 
entries that included a starting cluster number, and a linked list Granule 
Allocation Table (similar to MS-DOS FAT, and early Mac disk format)
DSDD, with 16 256 byte sectors per track  (320K)

The Epson Geneva PX-8 had an external 3.5" floppy available, and CP/M!
However, the PX-8 3.5" had 40 cylinders, with 67.5 tpi, instead of the 
common 80 cylinder 135 tpi of other 3.5" disks.
Those 40 cylinder 3.5" drives are quite rare.
I don't know about the track width; for reading, a PC can simply look at 
every other track.  And formatting a virgin disk and writing to it should 
work.  But, there is a definite possibility that RE-writing a PX-8 disk 
would result in one that the PX-8 couldn't handle (EXACTLY the same 
problem as RE-writing a 40 track 5.25" disk with an 80 track 5.25" drive)

With appropriate format handling software on the PC, it should be 
possible for a PC connected using your system to work with actual Epson 
diskettes, and emulate the Epson external drives.

Thank you for creating this!
Now, I wish that I had been able to keep the HC-20s!

Grumpy Ol' Fred     		cisin at xenosoft.com

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