debugger Posted April 13, 2004 Share Posted April 13, 2004 Sorry for always asking about programming stuff guys I'm reading the 7800 bios disassembly and i'm surprised about this: STA LF112 LF112 label is not defined in any place of the code or am i becoming crazy of reading too much 6502 asm lately? Did anyone tried to assemble again this file? Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted April 13, 2004 Share Posted April 13, 2004 Labels like that are usually generic labels corresponding to an absolute address in the original code. So if it weren't a STA, I'd say it was probably referring to something that's at F112 (or offset 0112 in a 4K ROM). But since I don't know which "source code" you are referring to, I can't say any more than that. I will say one thing about the 7800 ROM, though. One segment of it is meant to be copied down to RAM at $2300 hex, and is assembled to run at that address. So it won't make much sense if you look at it at the original address. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted April 13, 2004 Share Posted April 13, 2004 Look here for the 7800 BIOS source code. Incidentally, John Harvey pointed out to me a while ago that the 7800 BIOS ROM that's floating around the internet is actually slightly corrupted. I redumped it myself and got a slightly different checksum, now I just need to verify that my dump is accurate before I release it. Mitch Quote Link to comment Share on other sites More sharing options...
+Mitch Posted April 13, 2004 Share Posted April 13, 2004 OK, I did some more testing on my dump of the 7800 BIOS and it passed. So, for anyone still reading I'm included the "correct" version of the 7800 BIOS. Mitch a7800.zip Quote Link to comment Share on other sites More sharing options...
debugger Posted April 13, 2004 Author Share Posted April 13, 2004 Thanks a lot Mitch It does have two different bytes with the one i had Weird! The source code i have is the one here at atari age. I'll look into the pdf at the web you pointed me Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted May 6, 2004 Share Posted May 6, 2004 I've finished typing in and verifying the 7800 source code (7800source.asm) from the Atari Museum scans, and making the changes necessary for it to match up to the official ROM image. The synced version (7800rom.asm) produces an identical binary from my own assembler. Anyone who has a better scan and can read some of the missing comments is encouraged to speak up so we can get those added. There were three differences between the scanned version and the official version: 1) an extra "bad cart" test was added where $FFF8 in the cartridge had to be $F0 or greater, 2) changes to the 2600 cart transfer code, and 3) the checksum at $FFF8 was changed. As for the "LF112", that was a screwup in the disassembly, because that wasn't supposed to be a label. In fact, I don't even know why that address was chosen in the first place. It seems to be just for a delay, but maybe during development they had some external hardware that looked for the $F112 access to trigger a breakpoint or start a signal analyzer. 7800rom.asm.zip 7800source.asm.zip 1 Quote Link to comment Share on other sites More sharing options...
debugger Posted May 6, 2004 Author Share Posted May 6, 2004 Hello Bruce, thanks a lot for this, i'll take a look inmediatmently Quote Link to comment Share on other sites More sharing options...
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