Epson PX-8 Oval Display Adaptor

[ThinkpadIL]

What a great devices!!!

As I understand they are rare as unicorns. So my question - is it possible to recreate them?

 

[fjkraan]

So my question - is it possible to recreate them?

Based on the photo of the print, I think it should be doable. Most of the non-logic seems to be the TV-tuner and RS-232C level converter. Both the EF6803 and EF9545 are very informative. With schema's of other EF9545 applications, the video output can be found on other schema's of EF9545 applications. What is puzzling is the lack of any address decoder logic. So the address decoding is very rudimentary. The ROM is connected to the EF6803, the RAM to the EF9545. The EF6803 is probably used in mode 3, so it has only 128 bytes (internal) RAM, which is not much. A ROM disassembly should help.
What is not visible is the EF6803 crystal. Probably not a standard frequency, as it has to generate the Epson serial baud rate of 38400 Baud.
Attached is what I have so far.
Greetings,
Fred Jan

 

[Crashedfiesta]

Wow! Amazing work so far! Please let me know if you need more photographs or details of any components on the board. I'm more than happy to pop the board out and photograph the heck out of it if that would help.

 

[ThinkpadIL]

Based on the photo of the print, I think it should be doable. Most of the non-logic seems to be the TV-tuner and RS-232C level converter. Both the EF6803 and EF9545 are very informative. With schema's of other EF9545 applications, the video output can be found on other schema's of EF9545 applications. What is puzzling is the lack of any address decoder logic. So the address decoding is very rudimentary. The ROM is connected to the EF6803, the RAM to the EF9545. The EF6803 is probably used in mode 3, so it has only 128 bytes (internal) RAM, which is not much. A ROM disassembly should help.
What is not visible is the EF6803 crystal. Probably not a standard frequency, as it has to generate the Epson serial baud rate of 38400 Baud.
Attached is what I have so far.
Greetings,
Fred Jan

That's amazing! It will be great if in the end your efforts will evolve into a working device. I'll be glad to buy both of those devices (a UD-80 Video Display Controller and a DS-8 Device Switch).

 

[fjkraan]

Hi Crashedfiesta,

Here is my shortlist of wanted information:
- MPU crystal frequency,
- resistor array value,
- board backside,
- where is the button connected?

Greetings,
Fred Jan

 

[fjkraan]

In the ud80_rom7_11A ROM, one of the files to download is 'PIN-DRV.COM'. This could be the driver for the PX-4, 'PINE' is the name of the PX-4 board.

 

[Crashedfiesta]

Hi Crashedfiesta,

Here is my shortlist of wanted information:
- MPU crystal frequency,
- resistor array value,
- board backside,
- where is the button connected?

Greetings,
Fred Jan

Hi,

More pics below:







Hope those help! I have wired the 'new' switch onto the pads of the existing switch that is mounted directly to the board. The existing switch no longer works but seemed very weak to begin with.

Thanks,

Crashed.

 

[fjkraan]

Hi Crashed,

Thanks for the photo's. I still couldn't quite track the traces from the button to some processor pin, but my guess is, it is just the reset button. I couldn't find that on the photo's. At least is is enough to get a board created to test the schematic so far. Something simple without fancy multi-pin DIN connectors, but complete enough to test it. Maybe the disassembly will yield some clues, but MC801 is unknown mnemonic territory for me.
Greetings,
Fred Jan

 

[Crashedfiesta]

I took the DIN connector off (and replaced afterwards) so that the traces from the switch are easier to see. Hope they help!

 

[fjkraan]

Hi Crashed,

Thanks for the extra images. The button appears to be connected to the INT pin, not RESET. The boards are already on their way, so it is not the final version. I wasn't really expecting everything would be right the first attempt .

Greetings,

Fred Jan

 

[mk2s]

oh this is a neat project! I have a HC-80 and looking forward to seeing more about this.

 

[Fezzler]

Great pictures; it is cool to see the TF15. I fixed up a TF20 not long ago.

What is the difference between the TF-15 and TF-20?

 

[fjkraan]

The TF-20 boots from the disk, it is almost a CP/M system, just to serve files to the HX-20 or PX-8/4. The TF-15 has all the firmware in ROM. It would be cool to have a copy of the TF-15 ROM.

Fred Jan

 

[Crashedfiesta]

The TF-20 boots from the disk, it is almost a CP/M system, just to serve files to the HX-20 or PX-8/4. The TF-15 has all the firmware in ROM. It would be cool to have a copy of the TF-15 ROM.

Fred Jan

When I have some time I will see what I can do. I never thought to dump it when I first stripped it down to clean the drives...

 

[Fezzler]

The TF-20 boots from the disk, it is almost a CP/M system, just to serve files to the HX-20 or PX-8/4. The TF-15 has all the firmware in ROM. It would be cool to have a copy of the TF-15 ROM.

Fred Jan

I wonder if the TF-15 ROM can be inserted into the TF-20 and convert the TF-20 to a TF-15? Phew, that was a mouth full.

 

[fjkraan]

@Fezzler:
There is some technical information of both here: https://electrickery.nl/comp/tf20/doc/
Alas no schematic of the TF15, but I could try when the TF15 ROM becomes available.
The RAM is very limited in the TF15 (https://electrickery.nl/comp/tf20/doc/TechSuppManSec5.pdf, page 13), probably the reason it doesn't support the HX-20 file based commands (PX-8/4 does just reading/writing sectors, which is much simpler and easy to port to even an Arduino)
Fred Jan

 

[Crashedfiesta]

I'm hoping to get an hour or two free this weekend to get back out to the workshop (OK, it's a corner of my garage) and get the TF15 ROM out and dumped.

 

[Crashedfiesta]

Finally found the TF15 (how do you lose something so massive and heavy??) and got the EPROM out. Attached the dump in .BIN and .HEX formats. It's been a while since I used my ancient - but high quality and well respected - Dataman S4 but I think I got it dumped correctly...

Let me know how you get on!

 

[fjkraan]

Hi Crashedfiesta,
Thanks for the dump and the photo's.
The dump looked really weird after disassembly with z80dasm. Then I looked better at the photo's and the processor is a HD63A03. So the code is probably similar to the PF-10 and not at all like the TF-20. Oh, well it was worth the try. Maybe I find a better working 6800-family disassembler...
Fred Jan

 

[brijohn]

Hi Crashed,

Thanks for the extra images. The button appears to be connected to the INT pin, not RESET. The boards are already on their way, so it is not the final version. I wasn't really expecting everything would be right the first attempt .

Greetings,

Fred Jan

Hey Fred,

I'm curious if you have any update about your effort to reverse engineer the UD-80 board? I have a PX-8 in my epson collection and it would be nice to be able to connect it to an external monitor.

Brian