nesdev.org

Direct link: https://docs.google.com/file/d/0B4cc2TZRufDtWERQV2FHZFhFaU1odEdTbWlTTHB1REJRNXdr/preview Something I've never seen before. Unfortunately very little technical info. We get the RAM sizes, a note that the CD-decoder is a 6502 @ 4MHz with some bitmap conversion and sound table functions. ...

Nobody knows how the S-DD1 realizes when to begin decompression. Really? I remember reading a thread in this forum about how S-DD1 works, but I can't find it now. Besides, if Nevitski managed to convert the original code to a "S-DD1-less" code, I suppose he should know how it works I simu...

I'm pretty sure whicker is 100% right, and I always thought those pins' purpose what the same whicker told. Talking about this issue, I think S-DD1 decompression process could have been triggered by "monitoring" B-Bus pins. As most of you know, S-DD1 monitors any write to $4800 to begin DM...

The point is address pin numbers really don't matter if you organize the data accordingly. You don't have to shift SNES A16-A21 to ROM A15-A20 to utilize those 6 address pins when A15 needs to be skipped on the SNES. You can keep SNES A16 connected to ROM A16, and so forth. You just don't connect S...

I said ROM address pin A15, not SNES. Hi ROM connect ROM A15 to SNES A15, Lo ROM connect ROM A15 to the highest SNES pin you need. You're still ignoring SNES A15 when wiring to the rom address pins. The data would have to be programmed properly to allow for this rearrangement. I don't understand wh...

One trick would be to only swap the ROM A15 pin for the upper address bit you need. It would require the rom data to be re-arranged to support though. Another solution would be to program the memory so that A15 is don't care. That would save you quite a bit from needing to shift 8 bits with a mux. ...

So I guess my question should have been stated (and looks like already answered some) ... With rewiring, the 139 can work on hi rom carts AND lo rom carts with only minimal rewiring? Or is the re-wiring VERY different? Yes, it is very different; major difference is that /ROMSEL must not be asserted...

qwertymodo wrote:No, the 139 wiring is literally the only difference between hi and lo rom games, so it couldn't possibly be the same

That's right. But one more difference between LoROM and HiROM exists: A15 is not routed to MaskROM in LoROM games.

Worked flawlessly in more than 50 boards with 32, 24, 16 and 8 meg ROMs and with 256, 64 Kbit SRAMs:



Absolutely tested and 100% guaranteed.

My current '139 wiring design is this (traced this from a Zelda LTTP cart): 1. CART #49|||16. VCC 2. A20 (46) |||||15. '139 PIN 7 3. A21 (47)|||||14. A19 (45) 4. ROM /OE1 ||13. /RESET 5. NC |||||||||12. NC 6. NC |||||||||11. NC 7. '139 #15|||||10. NC 8. GND |||||||||9. SRAM /CE The LoROM wiring I p...

qwertymodo wrote:I guess my question was whether mask ROMs are asynchronous like SRAM. I was under the impression that they were not, and required a falling edge on CE or OE in order to latch the address lines.

Yes, ROMs are absolutely asynchronous, no edge needed to latch addresses.

Another tangentially related question. I've read a couple of places (including that FAQ) that the ROM CE and OE are both grounded. WTF? How does that even work? Aren't addresses latched at the falling edge of CE or OE, whichever comes last? So then how is it possible that both are grounded? both ar...

MottZilla wrote:Here is an old FAQ with pinout. http://www.snescentral.com/0/0/7/0077/sf2_faq.txt

There is very few new information on that FAQ that can prove what function has each GSU pin. Besides, the info is not really accurate... Clock Tower a Super-FX game?? WTF?

I suppose you saw my HiROM and LoROM cards on the web; I designed the cartridges so you can use both MAD-1 and 74LS139/74LS138 as ROM and RAM decoders. These are the photos for those who haven't seen them yet HiROM with MAD-1: http://imageshack.us/a/img850/3707/top5hg.th.jpg HiROM with 74LS139: http...

Those videos look absolutely fantastic i think this hack really deserves a try.

Could you post some information about your mod? I mean, the patch for disabling IRQ and the mod in the cartridge with the new crystal oscilator.