Search found 69 matches

by MrD
Fri Jan 03, 2020 7:32 pm
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 3342

Re: Most up to date Mega Drive cart pinout?

Ah, thank you! That makes more sense. I was working off a document that said /CAS0 was active in $000000-$7FFFFF (but that range is /ASEL, if I remember right). (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 out...
by MrD
Fri Jan 03, 2020 11:00 am
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 3342

Re: Most up to date Mega Drive cart pinout?

Thank you both. :) There are a few things that I'm still not sure of. Are the cart port's B28 !LWr and B29 !UWr asserted for the whole address space? Does B31 !Time being asserted by itself with no write indicate !OE from the !Time address region? (in other words TIME!CE = !TIME, TIME!OE = (!Time or...
by MrD
Tue Dec 31, 2019 11:33 am
Forum: Hardware
Topic: Most up to date Mega Drive cart pinout?
Replies: 6
Views: 3342

Most up to date Mega Drive cart pinout?

I'm troubleshooting my own cart design ( thread ), and one of the issues I'm having is that I don't have a good source for the Mega Drive cart pinout. There's lots of resources online, but they all seem to use different names for the same pins (is B16 named '/CAS0', '/RAS0', '/OE', '/C_OE', '/ROMO',...
by MrD
Wed Nov 20, 2019 8:38 am
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 16618

Re: Designing MD sdcard flashcart for fun, advice?

I've been fiddling with all of this again, and as is the way when you finish something, you discover something that lets you simplify it, possibly. All of the documents I can find for the 68000 say that its VIH minimum is 2.0V, which means that I ought to be able to interface it with the output of a...
by MrD
Sun Oct 27, 2019 4:07 pm
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 16618

Re: Designing MD sdcard flashcart for fun, advice?

Thank you for your time TmEE! What do you mean by cleanly supply the NOPs? That doesn't seem to apply in my method - I think I didn't explain it well :) After a write to a !TIME address takes place, the 68000 will jump to code in RAM, where it NOP delays first, then displays an animation and polls m...
by MrD
Sun Oct 27, 2019 2:58 pm
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 16618

Re: Designing MD sdcard flashcart for fun, advice?

Thanks :) I hadn't considered that the Flash writes might not work first time. Manually reading back the results to make sure they're copied right will be a pain... Apart from that though, does the glue logic make sense now I've accounted for combining !UDS and !LDS into a R/!W signal? And what sort...
by MrD
Sun Oct 27, 2019 1:40 am
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 16618

Re: Designing MD sdcard flashcart for fun, advice?

Very true. :) I was hoping that I'd get at a few thousand goes out of my test cartridge first though! My original plan was to use SRAM, but I couldn't find cheap 4 megabyte SRAM (as a x16 part or two x8 parts) in JLCPCB's parts list. I could have made it from 4 1Mbyte parts or something, but then I'...
by MrD
Fri Oct 25, 2019 2:50 pm
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 16618

Designing MD sdcard flashcart for fun, advice?

Hello, I'm designing a basic flash-style cart to read games and demos from an SD card and write them to flash memory, as an exercise. I'd like to get Titan's OVERDRIVE demo working as I've met some of the makers. :) I'm somewhat new to hardware engineering so I'd like a critical eye over my hardware...
by MrD
Mon Mar 31, 2014 5:15 pm
Forum: Blabla
Topic: Squee Wiki
Replies: 2
Views: 2536

Squee Wiki

Does anybody know what is going on with the MD wiki at squee.co?

It used to be my go-to source for easy to interpret MD information, but it's closed and whenever I visit the IRC it's been empty.
by MrD
Thu Feb 20, 2014 3:03 am
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

Thanks folks. I'm getting the same results on my PAL MD1 now. I'll have a look into the flickering cursor. Probably doing something foolish like not resetting the high VDP address bits for the cursor draw (but there's no high bit setting anywhere except VRAM clearing and TMSS, so I don't see where t...
by MrD
Mon Feb 17, 2014 7:14 pm
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

This version has VSRAM clearing, unused VDP register zeroing, and full VRAM address zeroing. Yet to be tested on my hardware, but I'm hopeful. :)

http://www.mrdictionary.net/stuff/2014/ ... tmaker.zip
by MrD
Mon Feb 17, 2014 1:26 pm
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

Right, that makes sense! I must have assumed that the last write was to an address with all VRAM high address bits zero. All my VRAM tile index entry writes for the interface work off that assumption. Thank you very much for seeing that. You're dead right about the VSRAM. I'm not used to there being...
by MrD
Mon Feb 17, 2014 6:36 am
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

Settings the unused registers to zero had no effect on hardware. I'm bamboozled. The pattern of the garbage shapes on screen makes me think that my VDP memory area assignments are wrong, but Regen's VDP debugger is showing me the VDP is interpreting the addresses correctly. lea (MM_VDP_CONTROL),a6 m...
by MrD
Mon Feb 03, 2014 10:13 pm
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

Thanks everyone, I'll have a look through my VDP setting routine and make sure I'm setting everything to some value once. I think I'm setting everything except the DMA registers to a good value. I didn't think these were read from unless DMA was enabled in $01 - Mode Register 2. Is it safe to set th...
by MrD
Mon Feb 03, 2014 12:10 am
Forum: Sound
Topic: Help with setting FM patch values
Replies: 34
Views: 18749

My code doesn't use DMA; I don't know how to use it yet. :) If you look at my code, the tiles in fact are copied excrutiatingly slowly to the VDP because I have to manually swizzle each byte on the 68000 as I retrieve it from the ROM (I'm using the exporter from the Usenti bitmap editor, it's for GB...