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 Post subject: VRC IV pinout
PostPosted: Sat Jan 28, 2012 6:42 am 
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As per board 352400 (iNES #25)
Code:
               .----\/----.
(n) PRG A13 -> |01      40| -  +5V
(n) PRG A14 -> |02      39| -  PRG A17 (r)
(s) PRG A2  -> |03      38| -> PRG A15 (r)
(s) PRG A3  -> |04      37| <- PRG A12 (s)
(n) CHR A12 -> |05      36| -> PRG A14 (r)
(n) CHR A11 -> |06      35| -> PRG A13 (r)
(n) CHR A10 -> |07      34| -> PRG A16 (r)
(r) PRG /CE <- |08      33| <- PRG D0  (s)
(n) PRG R/W -> |09      32| <- PRG D1  (s)
(r) CHR /CE <- |10      31| <- PRG D2  (s)
(n) CHR A13 -> |11      30| <- PRG D4  (s)
(n) CHR /OE -> |12      29| <- PRG D3  (s)
(n) CHR A10 -> |13      28| -> CHR A17 (r)
(n) PRG /CE -> |14      27| -> CHR A15 (r)
(n)      M2 -> |15      26| -> CHR A12 (r)
(r) CHR A18 <- |16      25| -> CHR A14 (r)
(n)    /IRQ <- |17      24| -> CHR A13 (r)
         NC -  |18      23| -> CHR A11 (r)
(w)WRAM /CE <- |19      22| -> CHR A16 (r)
        GND -  |20      21| -> CHR A10 (r)
               `----------'


Observations regarding board 352400:
At 352400 A2 and A3 are used to map the registers order instead of A0 and A1.
CHR A18 is connected to GND through a jumper and the mapper chip CHR A18 pin is left floating.

I suspect that VRCIV pin 18 is WRAM /WE for when battery backed memory is used. 352400 board has WRAM /WE connected straight to NES R/W,
(edit: disregard this, VRC mappers do not have write protection mechanism on WRAM)


Interesting stuff:
The pinout is eerily similar to that of the VRC2 chip as most of you already know.

What's funny about VRC2 is that it seems to have an microwire eeprom interface built in (93xx eeprom type) at the four pins marked "NC" at the wiki. Board number 351179 (Jarinko Chie as example of VRC2 cart I analyzed) I suspect it maps that microwire EEPROM interface to WRAM address space. Anyone know if it has been used for any game ?

microwire EEPROM pinout:
Code:

microwire EEPROM 93xxYY (93C66 for example)
       .--\/--.
CS  -> |01  08| -  +5V
CLK -> |02  07| -  NC
DI  -> |03  06| -  +5V
DO  <- |04  05| -  GND
       `------'


Last edited by l_oliveira on Sat Jan 28, 2012 9:42 am, edited 3 times in total.

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PostPosted: Sat Jan 28, 2012 7:29 am 
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That is not SPI but µWire EEPROM :P

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PostPosted: Sat Jan 28, 2012 7:43 am 
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TmEE wrote:
That is not SPI but µWire EEPROM :P


Ohhay ... Thanks for the correction. Editing ... ;)


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 Post subject: Re: VRC IV pinout
PostPosted: Sun Jan 29, 2012 10:15 am 
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l_oliveira wrote:

What's funny about VRC2 is that it seems to have an microwire eeprom interface built in (93xx eeprom type) at the four pins marked "NC" at the wiki. Board number 351179 (Jarinko Chie as example of VRC2 cart I analyzed) I suspect it maps that microwire EEPROM interface to WRAM address space. Anyone know if it has been used for any game ?



I seem to recall odd mentions of VRC2 / WRAM in the past, I searched thru old email, only thing I came up with was a blurb from Martin / Nestopia author:

Martin Freij wrote:
One thing I'm a bit unsure of is what's actually going on in $6000 on VRC2. Contra (J) writes $1 to it, reads back ANDed with $1 and crashes unless value is equal to $1. Could be a simple form of copy-protection I guess.


I couldn't come up with an answer at the time, as I hadn't come across the cartridge yet (I do have one now, but it's an epoxy version :( )

Having EEPROM mapped in there would seem to explain this behavior... I swear I recall other mentions of this as well, but this is all I can come up with at the moment.


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PostPosted: Sun Jan 29, 2012 10:34 am 
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Ah yes, this came up here not too long ago as well, that's why I remember...
http://nesdev.com/bbs/viewtopic.php?t=8274


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PostPosted: Fri Feb 03, 2012 7:39 pm 
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BootGod wrote:
Ah yes, this came up here not too long ago as well, that's why I remember...
http://nesdev.com/bbs/viewtopic.php?t=8274


About "Ganbare Goemon Gaiden: Keita Ougon Kiseru" SRAM, if you look at the board you will see an 74LS139 and an 74LS20. It appears that they are being used to create an /CE for the 6264 SRAM.

Also an Mitsumi MN1026 chip (That's NOT Microchip, that M is the newer Mitsumi logo, Bootgod... I can even give you datasheets for the chip if you want to have a look) powers and generates the non inverted CE to protect the SRAM contents.

Microwire interface pins are completely unused and disconnected on the Goemon board.

Also, it seems like botleg VRC2s do have SRAM decoder instead of Microwire interface. I'm designing some sort of "multi type development cart" with a VRC4 chip where I'll put some logic to automatically remap the address lines (like the pirate multicarts do with MMC3 banking for bigger roms) so I can run any VRC2/VRC4 titles without modifying the game program. I'll do testing with Gryzor and other "troublesome games".

I also intend to populate the EEPROM spot at the VRC2 board I have and maybe try to figure out how the Microwire interface works ... :)


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PostPosted: Sat Feb 04, 2012 6:46 pm 
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Yep Ganbare Goeman Gaiden has real SRAM, guess I'm not sure why byuu brought it up considering that. A while back I traced out the LS chips, trying to figure out an emulation bug that turned out to be an actual game bug: http://nesdev.com/bbs/viewtopic.php?t=6584

Looks like your right about it being a Mitsumi chip: http://www.logosdatabase.com/logo/m_73741170
Uncanny resemblance to Microchip 'M' logo. Anyways, fixed :)

I'd love to hear about the EEPROM details if you get it all figured out!


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 Post subject: Re: VRC IV pinout
PostPosted: Fri Feb 01, 2013 11:28 pm 
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Sorry about the necropost but:

Would anyone with a VRC4 pak and the ability to test be willing to see if the CHR registers are actually 9 bits wide? (See also: CHR A18 being present on oliveira's pinout) All that should be necessary is a copynes/kazzo and some kind of logic probe (e.g. resistor+led). It seems possible that the split CHR bank is arranged as [5 bits]:[4 bits], and so writing 0 followed by FF to all CHR registers should be an easy test.


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 Post subject: Re: VRC IV pinout
PostPosted: Sat Feb 02, 2013 2:03 am 
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Dragon Scroll(RC823) PCB 350603 KPC-4094V-0 also have place for EEPROM DIP8 chip.


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 Post subject: Re: VRC IV pinout
PostPosted: Sat Mar 02, 2013 8:14 pm 
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BootGod has obligingly tested: VRC4 does have 9 bit CHR registers, and so supports 512KiB CHR.


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 Post subject: Re: VRC IV pinout
PostPosted: Sun Jul 22, 2018 9:10 pm 
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Sorry to dig up such an old topic, but does anyone know if any games used 512KB of CHR?


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 Post subject: Re: VRC IV pinout
PostPosted: Sun Jul 22, 2018 9:29 pm 
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Only Metal Slader Glory (MMC5), and maybe some multicart things like Action 52, Maxi 15, etc. there's probably some modern pirate stuff that has CHR that large too. None of VRC4 though.

You can search by ROM size at Bootgod's database, but I think it will only do a combined search for PRG or CHR ROM larger than 512k so you gotta sift through the results. There aren't many that even used a PRG that size though, so it's not a huge list:
http://bootgod.dyndns.org:7777/


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 Post subject: Re: VRC IV pinout
PostPosted: Mon Jul 23, 2018 12:38 am 
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It is currently believed that the unlicensed VRC4 game "World Hero" uses 512K CHR and is otherwise a normal VRC4 clone.


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 Post subject: Re: VRC IV pinout
PostPosted: Mon Jul 23, 2018 12:51 am 
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I am a bit surprised that the VRC4 supports 512 KiB of CHR-ROM just like that when the supposedly more powerful VRC6 has to jump through hoops with its 2 KiB granularity mode.


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 Post subject: Re: VRC IV pinout
PostPosted: Mon Jul 23, 2018 1:09 pm 
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rainwarrior wrote:
You can search by ROM size at Bootgod's database, but I think it will only do a combined search for PRG or CHR ROM larger than 512k so you gotta sift through the results.
http://bootgod.dyndns.org:7777/


Yeah I did that, and it seemed that at most VRC4 games used 256K CHR. Figured I'd ask just in case I missed anything.

Was there any test roms for use with any of the VRC mappers?


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