Mask ROM pinout

Standard pinout PRG ROM - 16k / 32kB / 64kBytes (28pin)

This is the pinout Nintendo used for their PRGROMs, and it is compatible with EPROMs. For some unknown reasons, it was apparently required that unused adress lines on smaller ROMs were put to +5V, as Nintendo made different boards for each size (as opposed to place EPROMs of different sizes into the same slot). Some boards, such as CNROM, features solder pads in order to force those pins to +5V though.

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

Nintendo pinout PRG ROM - 128/256/512KBytes (28/32pin)

This is the pinout Nintendo used for most of their boards. It differs with standard EPROMs, and only have one enable line. This system allows for multiple sizes of ROMs on the same board. 128 KB ROMs are only 28 pins, they are shuffled 2 pins down, starting from pin 3 to pin 30.

On boards where A18 is never used, pin 2 is connected with pin 22.

             ---_---
      A17 - |01   32| - +5V
      A18 - |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 (/ROMSEL or mapper)
      A0  - |12   21| - D7
      D0  - |13   20| - D6
      D1  - |14   19| - D5
      D2  - |15   18| - D4
      GND - |16   17| - D3
             -------

Nintendo AOROM PRG ROM pinout - 128/256/KBytes (32pin)

Slight variant of the pinout above, where an additional enable line is used to prevent bus conflicts.

             ---_---
      A17 - |01   32| - +5V
(/ROMSEL) - |02   31| - CE (R/W)
      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 (/ROMSEL)
      A0  - |12   21| - D7
      D0  - |13   20| - D6
      D1  - |14   19| - D5
      D2  - |15   18| - D4
      GND - |16   17| - D3
             -------

CHR ROM - 8/16/32/64 KBytes (28pin)

This pinout is compatible with standard EPROMs, and is the same as for PRG ROM pinouts. However this time, unused address lines doesn't have to be put to +5V, and will be either NC (not connected) or +5V on boards where they are never used (where the mapper doesn't support larger ROMs)

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

CHR ROM - 128/256 KBytes (32pin)

This is the pinout Nintendo used for most of their boards. It differs with standard EPROMs, and with the Nintendo's PRG ROMs pinout. This system allows for multiple sizes of ROMs on the same board. Adress lines which are always unused on a board are put to +5V.

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

Standard pinout - 128/256/512/1024 kBytes (32 pin)

This is the standard pinouts for larger EPROMs. The vast majority (if not all) non-Nintendo made boards use those. In order to use a random EPROM in a Nintendo made board, it's necessary to compare this pinout and the pinout your board uses, and to cut traces/add wires to compensate for the differences. The name in parenthesis is for when the adress is unused (for smaller EPROMs).

                ---_---
A19 (or VPP) - |01   32| - VCC
         A16 - |02   31| - A18 (or PGM)
         A15 - |03   30| - A17 (or NC)
         A12 - |04   29| - A14
         A7  - |05   28| - A13
         A6  - |06   27| - A8
         A5  - |07   26| - A9
         A4  - |08   25| - A11
         A3  - |09   24| - OE
         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
                -------