Search found 899 matches

by Sik
Tue Nov 19, 2019 4:22 pm
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 28
Views: 5000

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

When you assert bus request, what you're doing is asking the Z80 to let its bus alone — which may take a bit of time, since it needs to finish any ongoing access first. You're supposed to read back from $A11100 to know when the Z80 has done that. The problem is that while the Z80 is reset it will ne...
by Sik
Tue Nov 19, 2019 3:16 am
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 28
Views: 5000

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

I've had it break (inconsistently… it starts making weird noises) when doing less than 192 cycles, so yeah. To be fair it's possible that the actual amount needed is less, but doing more doesn't hurt. From what I recall, I got the 192 cycles amount by looking at docs. Considering how some problems s...
by Sik
Mon Nov 18, 2019 7:50 pm
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 28
Views: 5000

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

It's… messier than that: https://plutiedev.com/using-the-z80#loading-z80 Or also from the Sega docs (though it's essentially describing the same thing): Z80 Start-Up Z-80 Operation Sequence: BUS REQ ON BUS RESET OFF 68k copies program into Z-80 S-RAM BUS RESET ON BUS REQ OFF BUS RESET OFF The bigges...
by Sik
Tue Nov 12, 2019 6:42 pm
Forum: Megadrive/Genesis
Topic: DMA and FIFO
Replies: 11
Views: 2076

Re: DMA and FIFO

The VDP control and data ports? Yes.

Emulators may handle them in a separate file since they're likely implementing them in the code handling memory accesses (which has no equivalent in real hardware, except maybe the bus itself), but emulators aren't necessarily modelling how real hardware works.
by Sik
Mon Nov 11, 2019 6:15 pm
Forum: SGDK
Topic: NOOB question - How do I get the frame count?
Replies: 8
Views: 280

Re: NOOB question - How do I get the frame count?

Yeah, sounds like you ended up looking something completely unrelated (・ω・;) Your own counters that go up every frame (like there) is the way to go, regardless of platform. Remember to not increment it while the game is paused. In a complex game you probably will even have multiple of those for diff...
by Sik
Fri Oct 25, 2019 8:19 pm
Forum: Demos
Topic: Street Fighter Alpha Mockup
Replies: 17
Views: 2372

Re: Street Fighter Alpha Mockup

You realize that 2×7KB×2 = 28KB which is almost half of VRAM, right? And also some of the bandwidth needs to be put aside for stuff like the sprite and scroll tables. Incidentally the method I described goes by the assumption that each character isn't uploading a new image every frame, and when they...
by Sik
Fri Oct 25, 2019 3:11 pm
Forum: Demos
Topic: Street Fighter Alpha Mockup
Replies: 17
Views: 2372

Re: Street Fighter Alpha Mockup

The CPS-2's resolution is tricky. Usually it's 384x224. It's got the same pixel height as an NTSC MD, but wider. Though was it treated as wide-screen or was it 4:3 in the arcades? It was 4:3 (with non-square pixels). 320x224 with 20% narrower sprites would be ok, but yeah 320x200 would be better. B...
by Sik
Fri Oct 25, 2019 10:25 am
Forum: Demos
Topic: Street Fighter Alpha Mockup
Replies: 17
Views: 2372

Re: Street Fighter Alpha Mockup

You can work around the sprite update issue by making sure only one updates at a time (e.g. if both need to update at once, then delay one of the players by one frame). Keep hitbox processing and momentum and such all working as normal, this only affects the sprite being shown on screen. I've tried ...
by Sik
Sun Oct 20, 2019 4:37 pm
Forum: Regen
Topic: What is commercial use?
Replies: 4
Views: 2655

Re: What is commercial use?

And this is why one should avoid writing "commercial use" as a blanket statement :​v Also I always find that one fun since distributing those ROMs is illegal in itself, but I guess the idea is to alert any unaware users who download it to see if somebody complains (and to make it clear you don't app...
by Sik
Thu Oct 17, 2019 7:52 am
Forum: Controls
Topic: New device letters
Replies: 20
Views: 2260

Re: New device letters

So I was looking at the Saturn standards doc for unrelated reasons and: https://i.imgur.com/4OqIb0D.png https://i.imgur.com/88z3B0s.png Turns out they do call it the 8-button pad (or at least they did it here). Go figure. I'd say to still stick to "j" for consistency though. Also something that hits...
by Sik
Sat Oct 05, 2019 7:11 pm
Forum: Controls
Topic: New device letters
Replies: 20
Views: 2260

Re: New device letters

That sounds like needlessly unpractical from a parsing viewpoint.

Honestly the only problem with lowercase is that it looks "ugly", which is probably a petty complaint :​P
by Sik
Sat Oct 05, 2019 3:01 pm
Forum: Controls
Topic: New device letters
Replies: 20
Views: 2260

Re: New device letters

The important part is that they're distinct byte values (and using lowercase actually does fulfil that requirement). The lawsuit with Sega was over horizontal scrolling, which Sega lost. Nintendo settled with Atari on the same thing out of court. The controller lawsuit from Atari was against Commodo...
by Sik
Fri Oct 04, 2019 5:34 am
Forum: Controls
Topic: New device letters
Replies: 20
Views: 2260

Re: New device letters

Yep, I even documented the pinouts: https://plutiedev.com/io-pinout Better yet, if you do it the other way (Mega Drive to Saturn), the SMPC will actually recognize some of the Mega Drive peripherals and a lot of Saturn games should be able to recognize them (albeit a 6-button controller won't have a...
by Sik
Wed Oct 02, 2019 10:45 am
Forum: SGDK
Topic: SRAM read / write
Replies: 12
Views: 903

Re: SRAM read / write

That will still need the game programmer to ensure that his code that calls SRAM functions aren't above 0x200000. Or enable SRAM from work RAM and disable before returning? :​P Changing the SRAM functions to work from sega.s makes them slower, but safe regardless of how they're used. Wouldn't it be...
by Sik
Wed Oct 02, 2019 10:38 am
Forum: Controls
Topic: New device letters
Replies: 20
Views: 2260

Re: New device letters

It's a completely different protocol (albeit they kept the button order similar… with R in place of where Mode usually goes). Mind, 6-button controller is the exception to the rule (and the reason why you have to include "6" only if the extra buttons are actually used for anything), pretty much ever...