Search found 293 matches

by Charles MacDonald
Sat Oct 31, 2015 9:35 pm
Forum: Megadrive/Genesis
Topic: M68K Interrupt Processing
Replies: 7
Views: 7893

Re: M68K Interrupt Processing

I had a similar problem in a non-Genesis related system. I posted on the Freescale forums a while back and learned that the autovectored interrupts are acknowledged synchronously to the E clock (as a remnant of using VPA for 6800-type synchronous bus cycles), and as the E clock can't be reset to any...
by Charles MacDonald
Fri Oct 30, 2015 7:26 am
Forum: Hardware
Topic: Game Toshokan
Replies: 10
Views: 12429

Re: Decapping more Genesis chips

Sik wrote:(what does Game Toshokan do, anyway? the only custom hardware in it is 128KB of RAM as far as I know)
Isn't the RAM for the games you download through the modem? Or is there something else weird about how the cart works?
by Charles MacDonald
Sun Oct 25, 2015 9:09 pm
Forum: Hardware
Topic: Decapping more Genesis chips
Replies: 17
Views: 62437

Re: Decapping more Genesis chips

For what matters, register $A11000 (the one that makes the console output a refresh signal on the cartridge slot) only works on early revisions, being a no-op on later versions. Aha, I never knew that and was wondering why my second-revision Megadrive was doing nothing special when using $A11000. :...
by Charles MacDonald
Mon Aug 17, 2015 1:41 am
Forum: Megadrive/Genesis
Topic: Using an Atari 2600 paddle controller in a genesis homebrew
Replies: 3
Views: 4119

Re: Using an Atari 2600 paddle controller in a genesis homeb

Does that mean a Genesis couldn't make use of the paddle controller no matter how it was programmed? That's right. The Atari systems that used the paddle had dedicated hardware for converting the the two analog inputs on the connector to a digital value for the CPU to read. For that reason it's not...
by Charles MacDonald
Wed Aug 12, 2015 5:23 am
Forum: Megadrive/Genesis
Topic: Sprite Isn't Showing Up
Replies: 35
Views: 21521

Thanks for the kind words! :D You're right, the link works now so I'll take a peek at the source and check out the framework BigEvilCorporation wrote.
by Charles MacDonald
Wed Aug 12, 2015 12:06 am
Forum: Megadrive/Genesis
Topic: Sprite Isn't Showing Up
Replies: 35
Views: 21521

The link to the source code doesn't work anymore.

Have you checked the code that writes data (namely the sprite data) to VRAM is working correctly? For example is the increment value in register $8F set to the right value?
by Charles MacDonald
Mon Aug 10, 2015 1:04 am
Forum: Hardware
Topic: FPGA version
Replies: 26
Views: 65977

I visited the idea: I can experience them out of MD environment. I can make testbench for TA-04 and TA-05. TA-06 too complex for this.
Very nice! Is there a reason why you are looking at the clone chips instead of the originals? Do the clone parts have some interesting or undocumented functions?
by Charles MacDonald
Fri Aug 07, 2015 4:09 pm
Forum: Hardware
Topic: FPGA version
Replies: 26
Views: 65977

This thread makes perfect sense. Especially when you see Analogue Interactive releasing a $500 - gorgeous - NES. The FAQ mentions that these systems are built up from old consoles using the original CPU and PPU chips that they cannibalized. I'm sure the HDMI video processing and such is nice, but i...
by Charles MacDonald
Thu Aug 06, 2015 4:34 am
Forum: Hardware
Topic: FPGA version
Replies: 26
Views: 65977

Re: FPGA version

While they all claim their versions aren't finished, i'll like to know if a FPGA (or a SoC) version of Genny is possible ? The SoC versions are just emulation running on an embedded platform, so it can be as good as the emulation they use (or steal :)) A FPGA version that is close to perfect is def...
by Charles MacDonald
Tue Jul 28, 2015 1:14 am
Forum: Megadrive/Genesis
Topic: DMA from ROM to CRAM, results are garbage
Replies: 15
Views: 12153

Re: DMA from ROM to CRAM, results are garbage

The source data in ROM can't cross a 128K boundary too, so maybe confirm the data is within a 128K block.

E.g. if the palette data starts at $05FFF0, the DMA will wrap to $040000 past $05FFFF instead of continuing from $060000 like you think it should.
by Charles MacDonald
Thu May 07, 2015 5:45 pm
Forum: Controls
Topic: Saturn = Genny ?
Replies: 3
Views: 8806

Re: Saturn = Genny ?

Yep, they are the same. Other than the connectors being physically different, the Saturn and Genesis controller ports are electrically identical. The polling is more involved for some of the Saturn peripherals, but it's no worse than accessing the Mega Mouse I suppose. With the right adapter you cou...
by Charles MacDonald
Sun Apr 26, 2015 4:03 am
Forum: Blabla
Topic: best emulator on android?
Replies: 7
Views: 11215

Ah yeah, of course i was using the free version... did not know it was based on Genesis Plus GX, i know it was also using some part of Gens code for the Sega CD emulation. I have the feeling he asked for permission to use parts of Gens Sega CD emulation as a cover for continuing to misuse Genesis P...
by Charles MacDonald
Sat Mar 28, 2015 12:52 am
Forum: Hardware
Topic: MOVEM quirk
Replies: 2
Views: 7960

Stef wrote:Interesting, does the extra cycle happen also with (An) indexing ?, i guess so ! That also explains why MOVEM.w Mem-->Reg is 12+4n cycles
when MOVEM.w Reg --> Mem is 8+4n cycles.
That's right, it happened when the source was (An), (An+), ($nnnn).w, etc. I tried all of the ones I could think of.
by Charles MacDonald
Thu Mar 26, 2015 6:09 pm
Forum: Hardware
Topic: MOVEM quirk
Replies: 2
Views: 7960

MOVEM quirk

I ran into an interesting problem when debugging software on a 68K SBC. When doing a memory-to-register transfer using MOVEM of any size (word,long) with any EA mode, it will read one extra address past the last legitimate location. This read is word sized even if transferring words or longwords. Fo...