interesting project : ECART

For hardware talk only (please avoid ROM dumper stuff)
Pascal
Very interested
Posts: 200
Joined: Wed Nov 29, 2006 11:29 am
Location: Belgium
Contact:

interesting project : ECART

Post by Pascal » Mon Jun 30, 2008 7:42 am

a pal of mine gave me this link about a really interesting project:

http://www.consolasparasiempre.net/proy ... /ECART.htm

the build a flash card on the expansion port. can be really usefull for building a debugger

HardWareMan
Very interested
Posts: 727
Joined: Sat Dec 15, 2007 7:49 am
Location: Kazakhstan, Pavlodar

Post by HardWareMan » Mon Jun 30, 2008 1:31 pm

When !CART signal goes low (log.0) then !CE0 signal works as chip select for cartrige, and !ROM signal on expansion slot is disabled (always log.1). And vice versa: when !CART goes high (log.1) then !CE0 is disabled (always log.1) and !ROM activates on lower 2MB address space. So, I don't get how he get access to cartrige while boot in his FLASH. That's possible only if make some change in MD schema.
Believe me, I know what I'm talking about. I made this:
HDD for MD.
Image
Boot OS cartrige for MD.
Image
And PS/2 keyboard controller to Joystick 2 port. Unfortunately, there are no fotos of it.
Image
BTW, MD get power thru HDD addon.

TmEE co.(TM)
Very interested
Posts: 2373
Joined: Tue Dec 05, 2006 1:37 pm
Location: Estonia, Rapla City
Contact:

Post by TmEE co.(TM) » Mon Jun 30, 2008 3:20 pm

Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.
Mida sa loed ? Nagunii aru ei saa ;)
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

Nemesis
Very interested
Posts: 773
Joined: Wed Nov 07, 2007 1:09 am
Location: Sydney, Australia

Post by Nemesis » Mon Jun 30, 2008 3:22 pm

:shock: Damn, HDD for a Mega Drive, now that's a mod and a half.

Nemesis
Very interested
Posts: 773
Joined: Wed Nov 07, 2007 1:09 am
Location: Sydney, Australia

Post by Nemesis » Mon Jun 30, 2008 3:23 pm

TmEE co.(TM) wrote:Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.
Do you know what the difference is? I've been doing all my tests on a 5313, but I have noticed most of my units have a 5313A.

HardWareMan
Very interested
Posts: 727
Joined: Sat Dec 15, 2007 7:49 am
Location: Kazakhstan, Pavlodar

Post by HardWareMan » Mon Jun 30, 2008 3:40 pm

TmEE co.(TM) wrote:Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.
What bug in 5313? But I can replace this 5313 by 5313A or even by clon TA-06.
PS Don't watch at those wires and MCs on PCB. Wires (and DIP switches) is for region, 50Hz/60Hz selection and M68K pause (by bus request). Those 2 MC is for auto generate signal !DTACK if it not generated in 16 VCLK clocks (for testing purpose and researching prohibited areas of address space).
Last edited by HardWareMan on Mon Jun 30, 2008 3:46 pm, edited 1 time in total.

TmEE co.(TM)
Very interested
Posts: 2373
Joined: Tue Dec 05, 2006 1:37 pm
Location: Estonia, Rapla City
Contact:

Post by TmEE co.(TM) » Mon Jun 30, 2008 3:44 pm

A friend showed me a video (don't remember where it is now) where you could see that when some sprite limitation is encountered, one of the background layers get affected too. Also, it seems that VDP access is slower, DMA is as fast as it should be, but I think direct access is not (5313 has more slowdown in games than 5313A). I've not pinpointed what is slower but something is slower.
Mida sa loed ? Nagunii aru ei saa ;)
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

HardWareMan
Very interested
Posts: 727
Joined: Sat Dec 15, 2007 7:49 am
Location: Kazakhstan, Pavlodar

Post by HardWareMan » Mon Jun 30, 2008 4:51 pm

Aahh. So that is not bug. That is its special opportunity. I don't get games hangs or graphics artefacts in games, so this is not bug.

How long ago it was....
Image

Mask of Destiny
Very interested
Posts: 591
Joined: Thu Nov 30, 2006 6:30 am

Post by Mask of Destiny » Mon Jun 30, 2008 6:34 pm

HardWareMan wrote:When !CART signal goes low (log.0) then !CE0 signal works as chip select for cartrige, and !ROM signal on expansion slot is disabled (always log.1). And vice versa: when !CART goes high (log.1) then !CE0 is disabled (always log.1) and !ROM activates on lower 2MB address space. So, I don't get how he get access to cartrige while boot in his FLASH. That's possible only if make some change in MD schema.
Believe me, I know what I'm talking about. I made this:
HDD for MD.
That is incorrect. The status of !CART changes the memory map, but does not disable either port.

When !CART is low, !CE0 is active from $0 to $3FFFFF and !ROM is active starting from $400000 (presumably to $600000). When !CART is high or left floating !ROM is active starting at $0 and !CE0 is active from $400000 to $7FFFFF. My cart dumping utility for the Sega CD relies on this behavior (well specifically that the cartridge gets remapped to $400000 when !CART is high). I believe there is one commercial cartridge, Flux Mega CD that relies on this behavior as well (AFAIK, it has !CART low and inits the Mega CD hardware manually).

HardWareMan
Very interested
Posts: 727
Joined: Sat Dec 15, 2007 7:49 am
Location: Kazakhstan, Pavlodar

Post by HardWareMan » Tue Jul 01, 2008 2:19 am

Mask of Destiny wrote:When !CART is low, !CE0 is active from $0 to $3FFFFF and !ROM is active starting from $400000 (presumably to $600000). When !CART is high or left floating !ROM is active starting at $0 and !CE0 is active from $400000 to $7FFFFF. My cart dumping utility for the Sega CD relies on this behavior (well specifically that the cartridge gets remapped to $400000 when !CART is high). I believe there is one commercial cartridge, Flux Mega CD that relies on this behavior as well (AFAIK, it has !CART low and inits the Mega CD hardware manually).
Very interesting... I don't knew that. But no way to control !CART pin from inside to swap expansion device and cartrige? I mean, boot from expansion port with storage (i.e. HDD or SD/MMC/CF), do something and then swap cartrige and expansion device in address map and boot cartrige. That is possible?

ElBarto
Very interested
Posts: 160
Joined: Wed Dec 13, 2006 10:29 am
Contact:

Post by ElBarto » Tue Jul 01, 2008 2:26 am

HardWareMan wrote: Very interesting... I don't knew that. But no way to control !CART pin from inside to swap expansion device and cartrige? I mean, boot from expansion port with storage (i.e. HDD or SD/MMC/CF), do something and then swap cartrige and expansion device in address map and boot cartrige. That is possible?
I think the Megacart do a trick like that with the helps of the CPLD or FPGA inside the cartridge but Fonzie could tell better than me.

Mask of Destiny
Very interested
Posts: 591
Joined: Thu Nov 30, 2006 6:30 am

Post by Mask of Destiny » Tue Jul 01, 2008 2:58 am

HardWareMan wrote:
Mask of Destiny wrote:When !CART is low, !CE0 is active from $0 to $3FFFFF and !ROM is active starting from $400000 (presumably to $600000). When !CART is high or left floating !ROM is active starting at $0 and !CE0 is active from $400000 to $7FFFFF. My cart dumping utility for the Sega CD relies on this behavior (well specifically that the cartridge gets remapped to $400000 when !CART is high). I believe there is one commercial cartridge, Flux Mega CD that relies on this behavior as well (AFAIK, it has !CART low and inits the Mega CD hardware manually).
Very interesting... I don't knew that. But no way to control !CART pin from inside to swap expansion device and cartrige? I mean, boot from expansion port with storage (i.e. HDD or SD/MMC/CF), do something and then swap cartrige and expansion device in address map and boot cartrige. That is possible?
As far as I know there's no way to swap the mapping in software. The only way to do what you suggest is to add some hardware to the cartridge (or mod the Megadrive/Genesis).

Nemesis
Very interested
Posts: 773
Joined: Wed Nov 07, 2007 1:09 am
Location: Sydney, Australia

Post by Nemesis » Tue Jul 01, 2008 4:28 am

It is possible to physically toggle the !CART line "on the fly" however, without any side effects. I've used a modified version of your dumping utility MoD to dump problematic devices (like the Sega Channel or the XBand modem) which have exotic address line decoding, and can only be dumped successfully when the cartridge is based at 0 on the memory map. The process I use is to load the dump utility into system RAM (so nothing from the MegaCD memory range is being relied upon at the time), then toggle the !CART line through a hardware switch, and dump data from 0x000000-0x400000, and it quite happily dumps the contents of the cart. If you had some kind of programmable switch which you could trigger through a write to a special address, which could disconnect and reconnect the !CART line at will, you could potentially load a routine into RAM, switch the state of the !CART line, and call back into code at the new locations.

I can't think of anything useful to apply this to at the moment, but I'm sure you could do something fun with it. It shouldn't be hard to make a simple loader cart which sits between a real cartridge and the Mega Drive, and has just this programmable !CART switch controller.

HardWareMan
Very interested
Posts: 727
Joined: Sat Dec 15, 2007 7:49 am
Location: Kazakhstan, Pavlodar

Post by HardWareMan » Tue Jul 01, 2008 10:49 am

Mask of Destiny wrote:As far as I know there's no way to swap the mapping in software. The only way to do what you suggest is to add some hardware to the cartridge (or mod the Megadrive/Genesis).
Exactly what I wanted to say.
Nemesis wrote:It is possible to physically toggle the !CART line "on the fly" however, without any side effects.
* * *
I can't think of anything useful to apply this to at the moment, but I'm sure you could do something fun with it. It shouldn't be hard to make a simple loader cart which sits between a real cartridge and the Mega Drive, and has just this programmable !CART switch controller.
Yes, I thought about this. We can take Mega Key and embed into it some logic, wich will accept data write at some address and pass it to !CART pin. So, MD or Cartrige do not need to change.
Hey, new dumper soon will born. Wich will do dumps directly to SD/MMC card (or CF card, if you need). No more link cables or big hungry HDD.... And process can be reversed (we can use SRAM instead cartrige). ;)

TmEE co.(TM)
Very interested
Posts: 2373
Joined: Tue Dec 05, 2006 1:37 pm
Location: Estonia, Rapla City
Contact:

Post by TmEE co.(TM) » Tue Jul 01, 2008 12:44 pm

Too bad SRAMs cost too much and are usually too small... I've got 2Mbytes worth of SRAMs, but total of 20...30 chips... for a while I could locally buy 4Mbit SRAMs, but not anymore :(
You could use Flash too, its not very problematic to write to Flash on MD (Megacart does it, so why can't we ;) )
Mida sa loed ? Nagunii aru ei saa ;)
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen

Post Reply