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A Big Hello!!!

Posted: Sat Jun 22, 2024 12:23 pm
by AndyJ
Hi! I'm Andy and I've just joined the forum.

Following on from Martin's suggestion, I'm introducing myself, saying hello and giving you a bit of my background - for what it's worth :)

I've been an avid computer programmer for over 45 years. My first taste of programming was when our school purchased a Research Machines 380z (Z80 based education / research device) whereupon I was introduced to BASIC. Not long after that, my first home computer was a Sinclair ZX81 that started my ultimate interest and fascination in machine code. I subsequently studied Electronics & Electrical Engineering and Computing Science.

I got my first bite at learning machine language in 1982 with the MOS 6502 on a Rockwell AIM65, followed by Commodore PETs 4032/8032. Subsequently, I went on to write games and demos on the Commodore 64 and Amiga platform (MC68xxx) I have also dabbled in the architecture of the TMS9900 (TI99/4a) and the 8080/8085 on PC. As far as microcontroller programming goes; it's mainly been C on the AVR (ATMega) platform. I also designed a Z80 based SBC and wrote the firmware.

Before my Electronics Lab (that took over four years to construct 2016-2020) was packed into boxes and put into the garage to make way for my young family, I managed to furnish it with thousands of 'retro' ICs (TTL/CMOS) vintage LED displays and so on. I used these chips (not CPUs) to design and build from scratch, a CPU and Instruction Set Architecture. This was my life goal since childhood. Not only had I managed to understand machine code, but had built a general purpose 'Turing Complete' machine.

Anyway, back to why I'm here: I recently acquired a pristine PSION Organiser II LZ64 and decided to get the rest of the set-up I'd need from Le Powerful Pierre (eBay) including the latest version of the CommsLink and various Datapaks and Rampaks (I already have a UV EPROM Eraser from my Lab to wipe Datapaks when needed)

I did buy a PSION Series 3a back in 1995 and noticed it had an OPL application available, but never used it as I was too busy working full time and doing a full-time three-year degree course in Computing Science (too much programming all around!) However, I did mess around with the unit and was mightily impressed with its specs and capabilities. I also bought a PSION Series 5 a couple of weeks ago and have just got that working with a Windows XP virtual machine.

My main interest lies in programming the 6303, but also to understand the benefits and importance of code reuse in existing ROM calls and routines. I will also need to learn OPL.

I would like to thank Martin and everyone who has put together and made available, all the resources we need at our fingertips!

I now have a lot of reading to do...

All the very best,


Re: A Big Hello!!!

Posted: Sat Jun 22, 2024 1:56 pm
by amenjet

Your history seems to mirror mine to a large extent, 380Z then ZX81, exactly the same...
Then some divergence.
Anyway. You mentioned your main interest is in the 6303, and I thought I'd point you to the assembler I made for the 6303 that is designed to do what the Psion assembler does, but on anything that can run Tcl, I use Linux. It needs a bit more documentation, but the source code is there.

To go the other way and disassemble 6303 machine code for the Psion, I created a sleigh extension for Ghidra that disassembles the machine code and also understands the Psion SWI calls.


Ghidra extension:

Hope this is useful.

Re: A Big Hello!!!

Posted: Sat Jun 22, 2024 2:40 pm
by AndyJ
Thank you for your very informative and helpful reply.

Interesting you had similar experiences to mine over the years.

A 6303 Assembler is great news and thank you for this information. These are hard to come by: I did read a forum (may have been stack exchange?) from someone looking for one, but could only find MASM/DASM that extensively used makros to provide the super set of 6303 instructions above the 6301. He wanted to use it to disassemble the ROM of a Yamaha DX-7 synthesizer.

Either way, I'll head over to github to retrieve your code and set that up!



Re: A Big Hello!!!

Posted: Sat Jun 22, 2024 7:05 pm
by amenjet
Let me know if you have any problems. I have used the assembler for a couple of small projects that I put into a datapack, well, a ROmin a top slot and an OPL program.
There's also hardware thingies for the Psion in some other repositories...

A Big Hello!!! - Welcome

Posted: Mon Jun 24, 2024 9:52 am
by Martin
Hi Andy and welcome

Peter 'the powerful pierre' alias thesourcerer is a long established member here as he has been on every Organiser II forum. The Comms Link and Rampaks you acquired are probably the ones that Andrew fabricated.

In case you haven't seen it, the republished technical reference manual is (here).

This is continually being updated as enthusiasts contribute to it. It was originally the brain child of Boris Cornet with contributions from Jaap Scherphuis. They created a section on the Dave Woolnoughs original PSION2.ORG web site. Evidence of which can still be seen (here)

As I say it is continually being updated. Members here Yves, Andrew and MartinP for example have contributed to the latest update above. Jaap has a version on his web-archive but he is not as active with Organiser II issues as he used to be. Subsequently his section doesn't contain the forum members updates.

You will find a PDF copy of Bill Aitken's Machine Code Programming on the manuals and books page above.

I look forward to seeing what you make of the Organiser II LZ.

Sincerely and in good faith

PS I'm chuffed to bits a genuine 'new user'

Re: A Big Hello!!!

Posted: Mon Jun 24, 2024 12:29 pm
by AndyJ
Hi Martin,

Thank you for the very kind and warm welcome!

Yes, I'm a genuine 'new user', albeit a bit late to the game and somewhat long in the tooth these days :D

I really appreciate the extra information and links you've provided, as this will allow me to further my knowledge and experimentations. I must say, that from what I've seen so far, I'm truly amazed by what the community has achieved with this device. I've been going through amenjet's software on github including his assembler (must have taken hours of coding to produce a masterpiece like that!) and also has pushed me to do a course in Tcl so I can understand what he's done - plus all the other projects available. It's quite humbling indeed.

I'll also have a good look through the Books Section when I get a moment as that's going to prove very useful.

Many thanks again,