interesting project : ECART
interesting project : ECART
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
http://www.consolasparasiempre.net/proy ... /ECART.htm
the build a flash card on the expansion port. can be really usefull for building a debugger
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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.
Boot OS cartrige for MD.
And PS/2 keyboard controller to Joystick 2 port. Unfortunately, there are no fotos of it.
BTW, MD get power thru HDD addon.
Believe me, I know what I'm talking about. I made this:
HDD for MD.
Boot OS cartrige for MD.
And PS/2 keyboard controller to Joystick 2 port. Unfortunately, there are no fotos of it.
BTW, MD get power thru HDD addon.
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Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.
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What bug in 5313? But I can replace this 5313 by 5313A or even by clon TA-06.TmEE co.(TM) wrote:Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.
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.
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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.
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That is incorrect. The status of !CART changes the memory map, but does not disable either port.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.
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).
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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?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).
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.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?
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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).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?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).
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.
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.
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Exactly what I wanted to say.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).
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.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.
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).
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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 )
You could use Flash too, its not very problematic to write to Flash on MD (Megacart does it, so why can't we )
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Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen