Search found 234 matches

by prophet36
Sun Apr 03, 2011 7:21 pm
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

Assuming I add /DTACK generation, are there any "safe" areas I can use? What about the $C00000 - $FEFFFF range? In theory I could get away with a small area (the monitor/menu program will probably only be a few kilobytes, and I can address the rest of my spare 4Mbyte RAM indirectly with some sort of...
by prophet36
Sun Apr 03, 2011 2:29 pm
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

Progress!

I got fed up with not having enough time to work on my own projects, so I quit my job :D Consequently, I've actually been making some good progress on this. If anyone's still interested in this, you can look here for details: http://www.makestuff.eu/wordpress/?p=1431 I'd quite like some ideas about ...
by prophet36
Sun Jul 18, 2010 11:30 pm
Forum: Hardware
Topic: Z80 access to cart address space?
Replies: 2
Views: 3292

Z80 does not strobe !AS by the looks of it

Partly answering my own question: it looks like the Z80 can read from the cartridge address space, but I'm not sure what the Z80 read cycles look like in detail. They appear to strobe !C_CE and !C_OE just as 68000 reads do, but not !AS.

Chris
by prophet36
Sun Jul 18, 2010 11:03 pm
Forum: Hardware
Topic: Z80 access to cart address space?
Replies: 2
Views: 3292

Z80 access to cart address space?

Hey guys, long time no see. I have a h/w question. Can the Z80 access the cartridge address space? If so, does the bus arbitration work to make Z80 reads look exactly like 68000 reads? Specifically is the timing with respect to the clock the same, and is !AS strobed as well as !C_CE and !C_OE? How i...
by prophet36
Fri Jun 12, 2009 1:16 am
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

Update...

Hi guys, Kaneda PM'd me to ask whether I'm still working on this project. The answer is yes , but following suggestions made by Graz I am redesigning it with an FPGA and an 8Mbyte SDRAM chip instead of the two 512kbyte SRAM chips. This has been taking longer than I'd like; I've been busy with other ...
by prophet36
Fri Dec 19, 2008 12:56 am
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

It's actually FAT32...I couldn't be bothered to implement FAT16 because it doesn't scale well to very large disks (for other projects). I don't have write support or long filenames working yet, which makes the menu a bit crap. But the AVR I use is quite nice...64k of flash, 4k onboard SRAM, loads of...
by prophet36
Thu Dec 18, 2008 9:46 pm
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

Update...I've got my menu system working. I used Stef's devkit, and I'm very impressed with how easy it is to use. From never having written any MegaDrive code, to having a working menu only took a couple of hours. Here's the menu image . It will run on an emulator OK, but the ROM select logic uses ...
by prophet36
Sat Dec 13, 2008 8:56 pm
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

Thanks Graz! Hmmm...FPGAs...never played with them. The closest I got is simple PALs, although I did work for 3Dlabs a few years ago doing VHDL validation. But there's a big difference between doing stuff as part of a big (and very talented) team and doing it all on your own. Have you done any FPGA ...
by prophet36
Sat Dec 13, 2008 8:17 pm
Forum: Hardware
Topic: USB MegaDrive DevKit
Replies: 32
Views: 27580

USB MegaDrive DevKit

*** Click Here for Progress Updates on the USB Megadrive DevKit! *** Hi, I've been working on this project on and off for a few months now, mostly as a training exercise in circuit design, homebrew PCB fabrication and programming microcontrollers. http://www.swaton.ukfsn.org/umdk/ Basically it's a ...