SNASM2 Debugger vs. Cross Products MegaCD kit

Reviving this thread since I've hit another snag. My ROM has exceeded 0x0001FFFF bytes, which means it's overrun the small Genesis RAM area the MegaCD provides without the /CART pin down.

The area 0x00000000 - 0x0001FFFF is supposed to be for the MegaCD BIOS, but one of the DIP switches allows me to map this for Genesis use. Unfortunately it's quite small, and I can't figure out how to trick the machine into thinking the CART pin is down so it'll give me the real Genesis memory map.

Inserting any old cart locks the debugger up, I think that overrides the DIP settings to boot from the debugging ROM.

This is treading far into unknown and undocumented territory now, all ideas welcome. One thing which might be of help is the MegaCD version of the SNASM2 manual, which I've only seen once in pictures here in the marketplace. Any idea who bought this kit, and if they'd be willing to scan in the manual? My version is the generic SNASM2 68000 and not the MegaCD specific one

 

According to page 2 of that marketplace thread, it was bought by user Teancum.
He also provides the following link where the MegaCD Documentation was already scanned, though not sure if it includes what you're looking for:
http://koti.kapsi.fi/~antime/sega/md.html

 

I think you might be having these problems because the system you're using isn't intended to debug cartridge based software.

 

Those are pretty awesome, thank you, but they're SEGA'S docs for the MegaCD and not Cross Products' docs for the kit. It seems to have a far detailed memory map in there which will be very handy, though!

Yeah I gave in to this from the start, but through perseverance it's been an invaluable tool for making my game. Most of my framework was developed with this thing so far!

Worst case scenario is that I'll have to continue developing features in small isolated test levels, and only build a full game ROM for emulation/burning to carts. I've only hit this ROM size limit because I've only just tried exporting an entire level for testing.

I suppose I could hunt down a kit more suited to my needs. I know there's a working Western Technologies setup that was demonstrated back in 2013 on here somewhere, I also have an original SNASM 68000 box which needs one of the interface units ASSEMbler has. Finding the docs and software is a bit more problematic though, this MegaCD kit is the only complete setup I could get hold of, and it wasn't cheap

 

You're a very crafty, creative guy.

 

What about inserting a flashcart into the cartridge slot, with the "CART" line taped over, similar to what you'd do when dumping a cartridge using the MegaCD dumping program Mask of Destiny created ( http://www.retrodev.com/transfer.html )? What will happen in this scenario is the cartridge will be mapped into 0x400000-0x7FFFFF into the memory map. You could compile the ROM using this base address, then write a loader into the mapped RAM region provided at 0x000000 to jump into the entry point for your ROM.

Note that you'll need a "basic" flashcart to make this work though, not one with dynamic memory or its own menu. You need one that actually presents just your code as hard data at a given address, from a cold boot. The best option here is the Tototek flashcart. If you don't have one, you can still buy it here:
http://www.tototek.com/store/index.php?main_page=product_info&cPath=1_6_20&products_id=59
There's still 5 in stock, better snap one up now if you want it, there'll never be another production run!

 

He could use the USA SEGA-CD or PAL MEGA-CD BIOS ROM and make it bootable with a CD boot sector, using your idea, Nemesis.

http://gendev.spritesmind.net/forum/viewtopic.php?f=5&t=1643&sid=39bd4b505893037ecdd39ec638eb209b

 

I experimented with an abandoned cart last night, cutting all the tracks except the CART pin. It seems this pin alone is enough to stop the target manager talking to the machine, though. Perhaps the MegaCD BIOS needs to run to initiate debugging. Although looking at the BIOS in the memory view shows a date of 2010 and one of the forum member's names, so something custom is already on here

I have one of these and some standard writable carts, which I believe is one of the most barebones flashcart setups available. It is possible to put the machine in a pure Genesis mode and get it to boot from any cart, unfortunately doing so kills all debugging capabilities, otherwise I could just burn my ROM to cart and debug it straight from that.

I'll have another crack at it this evening.

 

Would you mind dumping the BIOS and sending me a copy? It can't be one of the ones I did because I don't put my name on it. It could de Raq's original region free mod though, as he did put his name on the sub CPU BIOS.

 

Yep, I will do once I've figured out this MEGARUN.EXE thing for grabbing the BIOS.

It's this guy, by the way:

 

That's Raq's BIOS (PAL)

 

I promised you all this ages ago, better late than never I suppose:

 

I like the video. Neat demonstration.
It is a little fuzzy though, but I'm sure not one to speak, as when I go and record it's fuzzy like that too even when I record or watch my videos at 1080p.

I really need to learn 68k assembler.

 

The lens on my phone is scratched There's a more professional one coming soon via Computerphile's channel, recorded properly at the National Videogame Arcade in Nottingham. This one was more of a practice run (I'm a bit camera shy).

 

That makes more sense.

 

Ok, here's a more professional one!

 

I remmber repairing that dev kit of yours a few years back

 

Up for repairing an original SNASM breakout box, too?

Looks like some dry joints, and a slightly rusted power connector. I'd like to preserve whatever's on the EEPROMs though (if anything)!

 

Yeah sure thing mate i have my EPROM programmer handy