TGROM

TGROM (NES-TGROM and HVC-TGROM) is a common board within the TxROM set. Like other TxROM boards, TGROM uses the Nintendo MMC3 ASIC.

Overview

• PRG ROM size: 128, 256 or 512 KB
• PRG ROM bank size: 8 KB
• PRG RAM: None
• CHR capacity: 8 KB RAM
• CHR bank size: 1 KB and 2 KB
• Nametable mirroring: Controlled by mapper
• Subject to bus conflicts: No

Banks

• CPU $8000-$9FFF (or $C000-$DFFF): 8 KB switchable PRG ROM bank
• CPU $A000-$BFFF: 8 KB switchable PRG ROM bank
• CPU $C000-$DFFF (or $8000-$9FFF): 8 KB PRG ROM bank, fixed to the second-last bank
• CPU $E000-$FFFF: 8 KB PRG ROM bank, fixed to the last bank
• PPU $0000-$07FF (or $1000-$17FF): 2 KB switchable CHR RAM bank
• PPU $0800-$0FFF (or $1800-$1FFF): 2 KB switchable CHR RAM bank
• PPU $1000-$13FF (or $0000-$03FF): 1 KB switchable CHR RAM bank
• PPU $1400-$17FF (or $0400-$07FF): 1 KB switchable CHR RAM bank
• PPU $1800-$1BFF (or $0800-$0BFF): 1 KB switchable CHR RAM bank
• PPU $1C00-$1FFF (or $0C00-$0FFF): 1 KB switchable CHR RAM bank

Chips and pinouts

• PRG ROM - 2 MBits (256 kB x 8) (DIP-32)

                 ---_---
          A17 - |01   32| - +5V
          /CE - |02   31| - +5V
          A15 - |03   30| - +5V
          A12 - |04   29| - A14
          A7  - |05   28| - A13
          A6  - |06   27| - A8 
          A5  - |07   26| - A9
          A4  - |08   25| - A11
          A3  - |09   24| - A16
          A2  - |10   23| - A10
          A1  - |11   22| - /CE
          A0  - |12   21| - D7
          D0  - |13   20| - D6
          D1  - |14   19| - D5
          D2  - |15   18| - D4
         GND  - |16   17| - D3
                 -------

PRG ROMs of 1 MBit (128 kB x 8) comes in a DIP-28 packages are sit 2 rows back (only pins 3 to 30 are used). This pinout is not compatible with stantard 27C020 EPROMs, nor with standard 27C010 EPROMs, so to insert them in the board manual rewiring is needed.

• CHR RAM - 64 KBits (8 KB x 8) : Standard 6264 pinout.

• MMC3 pinout

See also

• Nintendo MMC3