Search found 261 matches

by TascoDLX
Tue Jun 25, 2013 12:29 pm
Forum: Megadrive/Genesis
Topic: Help figuring out some logic in Flicky - new challenge #3!
Replies: 19
Views: 11781

Hey matt, Here's the deal. The window bonus is given based on performance over every 8-round span, starting with round 3. If you earned it, it comes in the last of those 8 rounds. To get the bonus, you need to (for each stage): - deliver all the chirps at once - finish within the time limit (see bel...
by TascoDLX
Sat Dec 15, 2012 11:02 am
Forum: Megadrive/Genesis
Topic: M68000 Microcode-level emulation
Replies: 18
Views: 27973

The parameterization PLA has a 32-bit bus but the article seems clear that it is a 16-bit bus containing the operation word (IR register) and the other 16 bits are the complement of those. So maybe this isn't the 32-bit bus the address bus drives? You seem to be confusing the parametrization PLA wi...
by TascoDLX
Wed Jun 20, 2012 8:27 am
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

I have some idea how to handle this properly but I have difficulties understanding what hardware is really doing: why setting source address one word above would fix VDP slow read-out ? Does it mean the first word read is not read properly and instead written to the next VRAM address ? What about t...
by TascoDLX
Tue Jun 19, 2012 11:15 am
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

That's what I was doing before but it appeared it broke Willy Beamish Logo: see how it only rewrites reg 22 (and reg 23) but expects LSB to be reloaded with reg21 as well. If I leave reg21 to the final value it reached after previous DMA, I got those graphic errors. I see what it's doing. But if th...
by TascoDLX
Sat Jun 09, 2012 7:25 pm
Forum: Megadrive/Genesis
Topic: m68k subtraction and absolute value
Replies: 18
Views: 8975

In assembly, 'if a <> b then blah' becomes 'if NOT a <> b then branch'. So, in your case: * if e2 > -dy then blah becomes * if e2 <= -dy then branch That BGT (Branch if Greater Than) should be BGE (Branch if Greater or Equal). * if e2 < dx then blah becomes * if e2 >= dx then branch That BLT (Branch...
by TascoDLX
Sat Jun 09, 2012 6:55 am
Forum: Megadrive/Genesis
Topic: m68k subtraction and absolute value
Replies: 18
Views: 8975

So I attempted to port this: http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm#Simplification over to the genesis but for some reason it does not work correctly I have looked at each line of code at least 10 times each if not more and I can not understand what the problem is. In general, if...
by TascoDLX
Wed May 23, 2012 4:55 am
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

What I don't understand is what triggers those CDC host reads. I guess it's initially coming from a ROMREADxxx command sent to the BIOS but I can't seem to find what make the BIOS initialize CDC (CDCSTART command ?), enable buffer RAM writes for a few sectors then suddenly stop it (CDCSTOP command ...
by TascoDLX
Tue May 22, 2012 8:18 am
Forum: MegaLD
Topic: Emulating Pioneer LaserActive (Mega-LD) games
Replies: 189
Views: 141230

Excellent! In that case, I will add that I now have a fully working PAC -- Thanks to BlueBMW -- so I should be able to do minor testing should the need arise. Otherwise, I await the continued dumping efforts of Nemesis. ;)
by TascoDLX
Tue May 22, 2012 8:07 am
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

Well, I was wrong: in fact, running opcode by opcode does not make any good, the only thing that somehow made it go past the black screen on startup was to significantly increase either the number of SUB-CPU cycles executed per line (I forgot I still had this slightly modified in my previous test.....
by TascoDLX
Sun May 06, 2012 12:37 pm
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

So what you mean is that there is actually two values for DMNA, the one that can be read and the one that is written ? Yes, I would say there are different values across the board. As far as reads go: - RET and DMNA in 2M mode reflect the wordram assignment as usual. - RET bit in 1M mode reflects t...
by TascoDLX
Sat May 05, 2012 9:45 pm
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

I also have a question regarding Word-RAM and mode switching: to which part is assigned Word-RAM when switching from 1M to 2M mode ? I assume that if RET bit is set as well, it is set to MAIN-CPU side but is it the default ? What if RET bit is not set when MODE bit is changed from 1 to 0 ? Basicall...
by TascoDLX
Sun Apr 22, 2012 9:06 pm
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

That would be correct if that was to describe 32x32 mode - you need 4 horizontal 8x8 tiles to get 32x32 pixels. However, to make 16 horizontal pixels, you would need four 4x4 tiles. Hopefully any of that made sense. That would make a whole lot more sense if there was such a thing as a 4x4 tile. :P ...
by TascoDLX
Sun Apr 22, 2012 8:39 pm
Forum: Mega/SegaCD
Topic: Scaling hardware?
Replies: 84
Views: 47037

The stamps themselves are NOT laid out like tiles in the MD - the 16x16 stamp is actually laid out as sixteen 4x4 tiles. Each tile is like this 0 1 2 3 4 5 6 7 8 9 A B C D E F That doesn't sound right. Those should be 8x8 tiles (according to the manual). Otherwise, your description of the layout is...
by TascoDLX
Wed Apr 18, 2012 5:30 pm
Forum: MegaLD
Topic: Emulating Pioneer LaserActive (Mega-LD) games
Replies: 189
Views: 141230

(Tasco, your pac ended up being a LOT worse than it originally appeared to be! I'll get you pics later on. Dont worry, it'll be good when I'm done :) ) Cool. You are the man! Can't wait to see. ;) Also, I had a thought... It might be better to tap the LD video before it even reaches the chip where ...
by TascoDLX
Mon Apr 16, 2012 3:10 pm
Forum: MegaLD
Topic: Emulating Pioneer LaserActive (Mega-LD) games
Replies: 189
Views: 141230

Based on what I've seen, I would set the same value to 0138 as you do for 0139. I haven't found where 0138 is set, but I'm sure it's there somewhere. The settings I gave for 0139 should be correct.