robotrondev

How's it progressing with the NTSC guys? Drop me a mail at tunstals@hotmail.com if you got anything to show me

How you guys getting on with this? Any progress? Scott T.

Blueman I only really looked at the Robotron 2084 assembly because I was trying to write my own version in C# and wanted info on how the Enforcers operated. I now know Eugene Jarvis got that weird behaviour via a bug, and so reproducing that behaviour would be practically impossible without disassembling the 6809 arcade roms.... bah. I've not looked at the source for any other ROMs, but if there was one game I'd like to figure out the workings of, it'd be Xevious - but isn't that one fully commented anyway? I *loved* that game back in the day (I'm old enough to remember it when it was in the arcades first time round, and can still remember the intro music) . If Xevious needs reverse engineered in general, I can take a look, but really it's Robotron I'm interested in.

I'll take a look at the new source and if I have time, I'll add comments where applicable and post them back here for review. No promises though, you might have taken the disassembly further than I could hope However, any progress is good progress and I'll do what I can. Scott T.

Updated the disassembly and have most of the AI done. Bits left to do, I would still like help with the 7800 specific stuff like DLs, Zones and stamps etc. However, check out the disassembly and enjoy. It's really smart how so much was packed into so little space. If you spot any errors, let me know in this thread and I'll correct them. S. ROBOTRON.zip

Right, I got MESS front end and MESS set up. It's fantastic to see the registers updating in real time. I hope this will assist my reverse engineering endeavours.....

Eugene Jarvis himself said that there was a bug in the AI for them that he left in the code, and that's what created their cool behavior. Hard to reverse engineer something like that Yeah, I've taken a look at the 6809 disassembly for the arcade Robotron also. Never been a 6809 programmer so understanding what the code is doing, without comments, isn't easy. I wonder if the Atari 7800 developer had access to Eugene Jarvis' source code???

OK, I've made more progress. In fact, I've made a LOT of progress since last time. The original source code was a boon when working out what the lookup tables are and how they are used. I also managed to find the routines for every entity in the game, and have labelled them. I even have managed to map some of the labels from the original source code to the actual game source.. However, I'd really appreciate help here. If some of you guys who are into this as much as I am could peer review what I've written, or maybe fill in the blanks (esp. with respect to I/O port mapping: the sound, joysticks & graphics chips inc DLIs) I'd appreciate it a lot. There's some crazy carry-flag based stuff going on, and BEQs/BNEs where I don't see a zero-flag op before, and all kinds of stuff that needs a 6502 expert. There also are some tables that I don't know the purpose of, and I am sure once their purpose is known the rest will fall into place. If I could play Robotron 2084 on the Atari 7800 then just pause its state and inspect the memory I think I might have more of a fighting chance understanding what some of these magic tables are. But I don't know how. Anyway, I attach the latest source code. Dan Boris, if you want to upload this copy to your museum feel free. Slowly but surely I am getting there. Regards to all, Scott ROBOTRON.zip

I looked at that source code a while ago and to me it seems that it was for a version of MARIA (7800 video chip) that was never released in the consumer machine. Thanks for the improved reverse engineering listing. Does it build an exact byte to byte copy of the original? As far as I can tell, the updated listing is byte for byte, yes. It covers from $8000 - $FFFF in the address space so, yes I expect so. It's a 32K cart is it not? My next goal with the listing is to understand what the important zero page variables are, and also what some of the magic numbers are, e.g. in the sprite state tables. There are bit flags set which need decrypting.

Hi, I developed a version of Robotron 2084 for the PC a few years back using the Dark GDK and C#.NET . I never finished it though because I couldn't understand how the Enforcers and Tanks worked, their behaviour seemed pretty random. So fast forward a few years to now, I found out that Robotron 2084's Atari 7800 source was released... I took a look. I used to develop in 6502, Z80 and 68000 back in the day so wondered if I could reverse engineer the enforcer & tank logic and finally finish my game. As you probably know the source released on AtariMuseum for Robotron 2084 is *NOT* complete - it looks like an early build, there's a lot of code missing, e.g. the grunt to electrode collision detection. Then I found Dan Boris' disassembly of the final result and that shed a lot of light on the system. It was fantastic, because I couldn't find a 7800 rom disassembler that would deal with the .a78 file I had (I'm new to the Atari 7800). However, it still wasn't complete enough for my needs. So, I decided to reconcile the early source code with the finished source code, and with a bit of deduction work have expounded on Dan's work considerably. Not 100% but.... I attach the disassembly file, hopefully this will help others understand and maybe one day a full reverse engineering will be possible. Thanks to Dan Boris for getting the ball rolling and Atarimuseum for the original sources. ROBOTRON.zip