Epson CP/M floppy drives. Was: C64/C128 CP/M Cartridge Interest?

[Tony Duell]

> 
> > So the Floppy for the PX8 is specialized for a CP/M host it's not running
> > CP/M itself as there is not enough ram alone to qualify.
> To clarify the Epson floppy drive issue, there were three products:
> 
> TF-20 - Z80 based, 64k RAM, 2k ROM, boot from disk
> TF-15 - Z80 based, 2k RAM,  8k ROM, runs from ROM
> PF-10 - 6303 based, 2k RAM, 8k ROM, runs from ROM
> 
> The TF-20 supported the commands used by the HX-20 and the PX-4/8
> The TF-15 and PF-10 only supported the PX-4/8 commands.


Now that I didn't realise... I assumed that all drives worked with all 
machines. But the only one I have working is the TF20, which works with 
everything :-)

> 
> The TF-20 used the boot tracks of the disk to load some OS and a program 
> which made it a serial 'file server' for the host. The OS could very 
> well be a slimmed down version of CP/M.

I think it was close....

The following string exists in the OS on the TF20 system disk (the one 
that also contains HX20 disk BASIC, etc).

"Bdos Err On  : $Bad Sector$Select$File R/O$"

Sure looks like a CP/M message to me ... 

> The HX-20 commands are file based and were issued mainly from Basic. The 
> Basic
> extension is also on the boot disk.
> The PX-4/8 commands are sector based and issued from CP/M.

Although IIRC the disk BASIC for the HS20 had DSKI$ and DSKO$ commands 
(or something similar) to read/write absolute sectors.

There's also a free program for linux machines to emulate such a drive. 
Amazingly it works on my acient linux box, and from what I can remember, 
it works with the HX20 and PX4/8 machines. 

> All devices used the same protocol, epspd and baud rate. The same 
> protocol was used internally in the HX-20/PX-8 between the various 
> processors. The HX-20/PX-8 external video device also used it.

IIRC, at the hardware level it's RS232 voltages, 38400 baud. Probably 8 
bits, no parity, 1 stop. 
 
> The TF-15 and PF-10 are both ROM based. The TF-15 used the same housing 
> as the TF-20. As this resembled the QX-10 computer, the origin of the 
> TF-15/20 product was probably to provide two extra floppies for this 
> computer.

Of coruse the floppy drives in the TF20 (and maybe the TF15, I've never 
seen one) are the same voice-coil drives as in a QX10.

There's a 34 pin header on the nback of the TF20, which would appear to 
be for adding a couple of exter external drives. AFAIN, the software 
doesn't support it, though.

More interestingly, there's a parallel interface inside the TF20 (8255 + 
header), I can't remember if it's populated, or if the PCB is simply laid 
out for it. I have no idea what this was supposed to be used with.

The serial inbterface in the TF20 is a daughterboard. Whether other 
interfaces were planned to fit in place of it I don't know. 

I also have another Epson prodcut in a very similar case. it's called 
something liek a 'BM5'. The external interface is a DB25 socket, but it's 
not RS232, it's some custom patallel interface. Inside is a PSU, 
controller board and 5.25" floppy drive. But it's not a standard drive at 
all. The interface between the cotnroller and drive is a 34 way and a20 
way ribbon cable, the controller board has a _hard disk_ controller IC on 
it (one of the NEC ones). I believe the drive interface to be close to 
ST412, and the drive to take special floppies (possibly with servo 
tracks) and to have a rahter high capacity. I bought this thing 15 or so 
years ago (back when Greenweld sold interesting stuff) and have never 
been able to fidn out anythign about it. Oh well... It was probably a 
peripherals for the QX10 or something, but I have never seen an interface 
card for it.

-tony