MMC6 Mapper

[Valliefries]

I am simply here to ask if anyone tested the compatibility of whether or not the Save The Hero device's NES Adapter is compatible with MMC6.

As MMC6 was made exclusively for Startropics and Zoda's Revenge.

[kamalawala]

The MMC6 mapper is very similar to MMC3 apart from its 1K of PRG RAM and a couple different registers, so most of the existing code for MMC3 should work. There is code for detecting whether a cart is MMC6 (checking 0x3E00A for "STAR" in ASCII, present on both Startropics and Zoda's Revenge) and code for dealing with those different registers in order to read/write the 1K of PRG RAM when MMC6 is detected. By all means, it should work. However, I'm unsure whether it's been tested.

From NES.ino:

Detecting MMC6:

// MMC6 Detection
// Mapper 4 includes both MMC3 AND MMC6
// RAM is mapped differently between MMC3 and MMC6
void checkMMC6() {               // Detect MMC6 Carts - read PRG 0x3E00A ("STARTROPICS")
  write_prg_byte(0x8000, 6);     // PRG Bank 0 ($8000-$9FFF)
  write_prg_byte(0x8001, 0x1F);  // 0x3E000
  prgchk0 = read_prg_byte(0x800A);
  prgchk1 = read_prg_byte(0x800B);
  prgchk2 = read_prg_byte(0x800C);
  prgchk3 = read_prg_byte(0x800D);
  if ((prgchk0 == 0x53) && (prgchk1 == 0x54) && (prgchk2 == 0x41) && (prgchk3 == 0x52))
    mmc6 = true;  // MMC6 Cart
}

Reading RAM:

          if (mmc6) {                                                        // MMC6 1K
            write_prg_byte(0x8000, 0x20);                                    // PRG RAM ENABLE
            write_prg_byte(0xA001, 0x20);                                    // PRG RAM PROTECT - Enable reading RAM at $7000-$71FF
            for (word address = 0x1000; address < 0x1200; address += 512) {  // 512B
              dumpMMC5RAM(base, address);
            }
            write_prg_byte(0x8000, 0x20);                                    // PRG RAM ENABLE
            write_prg_byte(0xA001, 0x80);                                    // PRG RAM PROTECT - Enable reading RAM at $7200-$73FF
            for (word address = 0x1200; address < 0x1400; address += 512) {  // 512B
              dumpMMC5RAM(base, address);
            }
            write_prg_byte(0x8000, 6);                                  // PRG RAM DISABLE
          }

Writing RAM:

          if (mmc6) {                                                        // MMC6 1K
            write_prg_byte(0x8000, 0x20);                                    // PRG RAM ENABLE
            write_prg_byte(0xA001, 0x30);                                    // PRG RAM PROTECT - Enable reading/writing to RAM at $7000-$71FF
            for (word address = 0x1000; address < 0x1200; address += 512) {  // 512B
              myFile.read(sdBuffer, 512);
              for (int x = 0; x < 512; x++) {
                write_wram_byte(base + address + x, sdBuffer[x]);
              }
            }
            write_prg_byte(0x8000, 0x20);                                    // PRG RAM ENABLE
            write_prg_byte(0xA001, 0xC0);                                    // PRG RAM PROTECT - Enable reading/writing to RAM at $7200-$73FF
            for (word address = 0x1200; address < 0x1400; address += 512) {  // 512B
              myFile.read(sdBuffer, 512);
              for (int x = 0; x < 512; x++) {
                write_wram_byte(base + address + x, sdBuffer[x]);
              }
            }
            write_prg_byte(0x8000, 0x6);                                // PRG RAM DISABLE
          }

Sidenote: Is there any particular reason for setting 0xA001 to 0x20/0x30 and 0x80/0xC0 separately instead of setting it to 0xA0/0xF0 and reading/writing the 1K of RAM in one go? Is it safer?

[Cephiros]

Working under the assumption that the savethehero adaptor maps to the same pins that the 6slot uses, I can verify both startropics, and startropics2 dump correctly. There was a quirk on 9.5 where it did not see sram, But if I set the mapper information and sram manually, the saves dumped correctly as well. this may have been fixed already in 10.2, I have not tested it.

[kamalawala]

Thanks for the confirmation!

[wesclemens]

I can confirm this is still an issue in 12.3 manually setting the mapper does work. Only option is 8K but it creates the 1K dump correctly.

[sanni]

Could you post log the file?

[wesclemens]

Manually set was able to dump sram: CART.txt
Picked from DB was not able to dump sram: StarTropics.txt