Search found 911 matches

by Sik
Thu Jan 16, 2020 11:04 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

That's the expansion port rather than the cartridge slot. Does that make a difference? I don't think so, many of the signals are shared between the two (and some of the Mega Drive components too), e.g. /CAS0 acts as the output enable for everything that isn't work RAM (for some reason work RAM gets...
by Sik
Thu Jan 16, 2020 12:44 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

Black starts at 25mV above ground and goes up to 800mV with more or less exactly 25mV steps on red and green channels, but blue channel is about 20mV lower in full scale amplitude, which explains the subtle yellow tint compared to MD output that is seen on all 32X I have had access to. 3 2 X Anyway...
by Sik
Wed Jan 15, 2020 5:30 pm
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

*wonders if Tiido noticed that edit* Alright, still trying to understand what /CAS2 does no matter how many times I get it explained x_X So far all I can seem to understand for sure is that /CAS0 asserts before it and that /ASEL is somehow involved (not sure about /ASEL's timing though). Oh, and th...
by Sik
Thu Jan 09, 2020 4:21 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

OK this kinda stalled. Forgot to mention that when the Master System stuff was probed the video signals remained intact (if useless due to being stuck with a H40 clock), so there goes the whole deal with EDCLK, /HSYNC, /VSYNC and /YS. Was discussing this in Plutiedev and our guesstimation from that ...
by Sik
Mon Jan 06, 2020 5:23 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

I suppose it would be nice to know what range the 32X outputs on the audio lines (though I heard reports that the 32X's output may be a bit too loud). It is the one piece of official hardware that makes use of it. Also the cartridges with YM2413 seem to use its output directly (?) so maybe looking a...
by Sik
Sun Jan 05, 2020 6:42 pm
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Re: Cartridge slot questions

That still doesn't tell me what voltage range you should use to keep the audio signal in a "reasonable" range (I'm not a Mega Drive circuit expert :v), only that it's mixed as-is with the rest of the audio (my initial guess would be that the ideal range would be ±1V but honestly I could be wildly wr...
by Sik
Sat Jan 04, 2020 8:49 pm
Forum: Hardware
Topic: Cartridge slot questions
Replies: 22
Views: 1064

Cartridge slot questions

Here I am trying to document the cartridge slot because it turns out that trying to find anything is a pain in the ass (let alone anything accurate). No wonder this thread exists. The function of the pins in Master System mode is woefully underdocumented. Those that are the same function are easy to...
by Sik
Fri Jan 03, 2020 9:26 pm
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 515

Re: Most up to date Mega Drive cart pinout?

(Also confusing me is that the Sonic 3 cart uses !TIME as the clock to a D-type register for bankswitching without combining it with an output enable or read strobe.) I don't think it ever bothers to read back the value (only write), makes sense that it won't allow reads from it. They were trying t...
by Sik
Fri Jan 03, 2020 6:08 pm
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 515

Re: Most up to date Mega Drive cart pinout?

Are the cart port's B28 !LWr and B29 !UWr asserted for the whole address space? As far as I know, yes. /UWR is for the upper byte, /LWR is for the lower byte (i.e. they're the write enables for each half of the word). For byte accesses only one is asserted, for word accesses both are asserted. Does...
by Sik
Wed Jan 01, 2020 5:56 am
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 515

Re: Most up to date Mega Drive cart pinout?

This is something I should have documented in Plutiedev long ago… eh. I'll try to get around that soon. Leaving this here meanwhile (B side is the front of the cartridge): https://i.imgur.com/gNLSkhs.png I was going to write a list of everything but I have doubts about some lines (I'm not the expert...
by Sik
Thu Nov 28, 2019 10:56 am
Forum: SGDK
Topic: m68k at risk of being dropped from gcc 11
Replies: 7
Views: 1799

Re: m68k at risk of being dropped from gcc 11

Shame I can't get it to show what was the final bounty amount (I'm probably doing something stupid?). I remember it had reached $6000 some days before it was claimed.
by Sik
Wed Nov 27, 2019 1:04 am
Forum: Tools
Topic: Aseprite Mega Drive Digitizer
Replies: 10
Views: 2296

Re: Aseprite Mega Drive Digitizer

I think I've seen emulators go that far to emulate composite, but it still fails to account for differing TV comb filter quality and such. Also there's the problem where these days you can't reasonably predict what the output method will be, to be blunt. Some people may just grab the original cables...
by Sik
Tue Nov 19, 2019 4:22 pm
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 28
Views: 6871

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: 6871

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: 6871

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...