Adoption of software from Motorola MC680X based computers to Epson HX-20 - Is it possible?

[ThinkpadIL]

Epson HX-20 laptop has a Hitachi HD6301 CPU (actually two of them). From what I've read on the Internet, it is software-compatible with Motorola's MC6801 CPU.

So, my question is, whether it is possible to adopt a software written for MC680X CPU based computers to Epson HX-20? And if the answer is YES, did anyone try to do it?

 

[CamiTheWitch]

It’s definitely possible, but it may have ended up being more effort than just outright writing code for the HX-20, since a lot of memory addresses and such would need to be changed, as well as methods to access stuff like the display.

I’m almost positive someone tried to do it, but they may have kept the resulting program private, either because it didn’t work right or because they were worried about copyright or something. I couldn’t find any software I could easily identify as a port when looking through some of the software collections for the HX-20, but it definitely doesn’t mean nobody did it.

 

[krebizfan]

Given the development time for the HX-20 with the system showing up soon after the first production 6301s, the system software almost certainly had to be ported from 6800. Doing it now given the poor documentation available in English may be a great challenge. I can't find a good Japanese page that lists possible sources for software tools to work on the HC-20.

 

[ThinkpadIL]

Here are some links to webpages offering 6301 development tools that may be useful:

6301 Assembler for Windows

Open Source

MIDI Programs Page

www.hermannseib.com

http://john.ccac.rwth-aachen.de:8000/as/

 

[Martin Hepperle]

Depending on how much interaction with the hardware is required, this shuld be quity easy.
For example the FORTH ROM for the HX-20 is derived from the figForth source code for the 6800.
The 6301 is almost identical to the 6800. The 6809 has a few additional registers, so that backporting from 6809 ro 6301 is more difficult.

I used the "A09" assembler to assemble some binary programs to be called form BASIC as well as for recreating the FORTH ROM.

The Technical Manuals describe the hard- and firmware of the HX-20 in detail (see F. J. Kraan's web site https://electrickery.nl/comp/hx20/index.html).
Adapting to the host might require more effort (16...32KB of RAM, small screen, mass storage concepts, serial interface access, ...) , but the Technical Manuals describe all relevant entry points, data structures and protocols.

 

[ThinkpadIL]

Yes, small screen is one of the limiting factors. Though there are video adapters allowing to use a larger visible screen area.

 

[Martin Hepperle]

Here is a table of 6301 op codes - lifted from the book by E. Balkan "Using and programming the Epson HX-20 portable computer". This book contains a small section on assembler programming.

 

[fjkraan]

@Martin: Thanks for the title of the book, I found a scan of on the internet and added it to the doc page: https://electrickery.nl/comp/hx20/index.html. I also re-found the image of the native HX-20 Assembler/Debugger: https://electrickery.nl/comp/hx20/Julian_Wald/items.html on my harddisk.

 

[ThinkpadIL]

HX-20 Assembler/Debugger:

@Martin: Thanks for the title of the book, I found a scan of on the internet and added it to the doc page: https://electrickery.nl/comp/hx20/index.html. I also re-found the image of the native HX-20 Assembler/Debugger: https://electrickery.nl/comp/hx20/Julian_Wald/items.html on my harddisk.

HX-20 Assembler/Debugger and the manual is a really great find. Some time ago I've found some page (http://oldpc.su/eps/eps_roms.html) where at some point were supposed to be uploaded some very interesting ROMs and documents but unfortunately till this day there are only links with no files.

By the way, is there on the Internet any good reference on how to burn HX-20 ROMs with available today hardware and where to get suitable ROMs?

 

[fjkraan]

Programming is a simple as loading the file with the support program for the programmer (the TL866 Plus is still available and there is even software for Linux). These devices and the EPROMs are available cheap from ebay or similar. The 27C128 CMOS EPROM is preferred for a battery based computer like the HX-20. The 27C128 will work in the Expansion Unit (https://electrickery.nl/comp/hx20/memoryMap.html). The HX-20 internal socket will support only an 8 kByte EPROM (27C64) for the Assembler only (first half of the image).

 

[Martin Hepperle]

@Martin: Thanks for the title of the book, I found a scan of on the internet and added it to the doc page: https://electrickery.nl/comp/hx20/index.html. I also re-found the image of the native HX-20 Assembler/Debugger: https://electrickery.nl/comp/hx20/Julian_Wald/items.html on my harddisk.

Thank you for the update of your web site!
The manual for the assembler is really interesting and the assembler looks very professional. I have not yet tried it, but surely will...