Search found 820 matches

by Eke
Tue Oct 24, 2017 3:01 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 834
Views: 284126

Re: New Documentation: An authoritative reference on the YM2612

Some more news about YM2612 DAC "ladder" effect: a guy named Nuked who analyzed YM3438 die shots recently wrote a cycle-accurate implementation in C and figured the effect was actually caused by two things: 1 ) the fact that the resistor array would not exactly reach Vcc/2 on either negative or posi...
by Eke
Tue Oct 24, 2017 8:43 am
Forum: Controls
Topic: XE-1AP
Replies: 3
Views: 439

Re: XE-1AP

Yes, it was mostly emulated by reversing the various games that use it and then later completed (the unused buttons mostly) using some XE-1AP driver code that was posted on sega-16 http://www.sega-16.com/forum/showthread.php?30101-XE-1AP-Analogue-Controller-Cyber-Stick-CZ-8NJ2-XE-1AJ-Driver-%28Sourc...
by Eke
Sun Sep 24, 2017 10:41 pm
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 32
Views: 4167

Re: Undefined behavior for ABCD and SBCD

Small update to flamewing's test to trigger a bug in Genesis-Plus-GX at least: https://github.com/flamewing/68k-bcd-verifier/pull/1/commits/8e917e6a6dffe4724c6432c10efde0e3afd720bf http://notaz.gp2x.de/md/rel/bcd-verifier-u1.zip Well, this was indeed a very stupid bug in Musashi: upper bits of NBCD...
by Eke
Sat Sep 09, 2017 9:05 pm
Forum: Mega/SegaCD
Topic: X-Eye Service Manual and Technical Manual
Replies: 3
Views: 410

X-Eye Service Manual and Technical Manual

I don't know if those are already known but I found these manuals recently https://console5.com/wiki/File:JVC_X%27Eye_RG-M10BU_Service_Manual,_No._20478,_April_1994.pdf https://console5.com/wiki/File:JVC_Technical_Manual_X%27Eye_RG-M10BU,_1994.pdf They are quite interesting to read compared to other...
by Eke
Tue Aug 29, 2017 8:40 am
Forum: Megadrive/Genesis
Topic: VDP DMA fill in Ballz 3D; not writing fill byte
Replies: 11
Views: 624

Re: VDP DMA fill in Ballz 3D; not writing fill byte

That's not it, no. Let's ignore Ballz 3D and presume a test ROM: We set up for a VDP DMA fill operation and set CD5, but then we don't write the fill byte. And there's no FIFO slots available to pull it from, the FIFO is totally empty. Instead, we poll the VDP status bit 1 (DMA) waiting for it to b...
by Eke
Tue Aug 22, 2017 8:17 am
Forum: Megadrive/Genesis
Topic: Interlace mode (LSMx=3)
Replies: 20
Views: 911

Re: Interlace mode (LSMx=3)

What I think you are missing, as far as I can tell: - for vscroll, value read from VSRAM must be shifted right by one (VSRAM width is 11-bit but bit0 is ignored in interlaced mode 2) before being added to vcounter value (9-bit) - for sprites, when preparing the sprites list (i.e looking which sprit...
by Eke
Mon Aug 21, 2017 11:13 pm
Forum: Megadrive/Genesis
Topic: Interlace mode (LSMx=3)
Replies: 20
Views: 911

Re: Interlace mode (LSMx=3)

What I think you are missing, as far as I can tell: - for vscroll, value read from VSRAM must be shifted right by one (VSRAM width is 11-bit but bit0 is ignored in interlaced mode 2) before being added to vcounter value (9-bit) - for sprites, when preparing the sprites list (i.e looking which sprite...
by Eke
Tue Jul 11, 2017 10:18 pm
Forum: Controls
Topic: Mega Mouse Usage
Replies: 16
Views: 1962

Re: Mega Mouse Usage

Yes, that's pretty much it :wink:
by Eke
Tue Jul 11, 2017 10:10 pm
Forum: Video Display Processor
Topic: Is DMA Fill buggy?
Replies: 11
Views: 585

Re: Is DMA Fill buggy?

The 'issue' is that VRAM byte writes (used by VRAM fill and copy DMA) actually occur to VRAM address ^ 1 so you can get unexpected results depending on start address, DMA length and increment alignments. In your case, when VRAM address reaches F000H, last write occurs at F001H instead of F000H. I th...
by Eke
Mon Jul 10, 2017 12:10 pm
Forum: Controls
Topic: Mega Mouse Usage
Replies: 16
Views: 1962

Re: Mega Mouse Usage

I can't really tell what you're doing from the values, but 3-line handshake is simple: start with unselected (0x60), then toggle back and forth between the two selected states (0x20 and 0x00) to get nibbles (0x20 first). That's all there is to it. When you're done, deselect the mouse again (0x60). ...
by Eke
Sun Jul 09, 2017 11:08 pm
Forum: Controls
Topic: Mega Mouse Usage
Replies: 16
Views: 1962

Re: Mega Mouse Usage

I'm guessing the oo means it timed out? Yes. It seems to indicate the mouse does not respond to handshake request when TH is low unless it was properly reseted (60h followed by 20h or possibly 00h). If you don't mind, I added a few write sequences for completeness in this test ROM. This should be t...
by Eke
Sun Jul 09, 2017 8:06 pm
Forum: Controls
Topic: Mega Mouse Usage
Replies: 16
Views: 1962

Re: Mega Mouse Usage

Thanks for this quick test. And yes, it's just a one shot write sequence , it's not supposed to update itself. Results are interesting but definitively not what is expected from games (and quite different from what you get in emulators). I suspect the reason is I'm switching TR output too fast for t...
by Eke
Sun Jul 09, 2017 12:36 pm
Forum: Controls
Topic: Mega Mouse Usage
Replies: 16
Views: 1962

Re: Mega Mouse Usage

Sorry to bump this thread but anyone here having a Sega/Mega Mouse could test this ROM on hardware (with mouse controller plugged in port 2) and report output values ? I'm trying to figure the acknowledge latency of the mouse protocol, as it seems to be (involuntarily ?) needed by a few game routines.
by Eke
Fri Jun 23, 2017 1:10 pm
Forum: Hardware
Topic: HDD (or flash) instead of a CD, questions...
Replies: 140
Views: 27029

Re: HDD (or flash) instead of a CD, questions...

It's not exactly the same (it push Q first, not P) but i think I got it know, based on previous post Beware that this last diagram is about different signals (SQCK/SQDT)- also present on CXD2500 chip (the latter is just named SQSO) - which are dedicated to Q-channel (with CRC verification): that wa...
by Eke
Tue Jun 20, 2017 12:08 pm
Forum: Mega/SegaCD
Topic: Subcodes only for CD+G ?
Replies: 7
Views: 491

Re: Subcodes only for CD+G ?

If the SBSO line is flat, it won't bug the game ? It shouldn't affect software since, from my testing in emulator, neither games or BIOS care if the subcode interrupt never occurs But it's possible it could lock the ASIC and thus the whole Mega CD hardware, depending how it was designed. Quite unli...