INES Mapper 029

This mapper was allocated on 15-nov-2013 by a mysterious jerkface to implement some homebrew games, including Glider. FCEUX acquired support on r3029.

The example board in question was marked as follows: "Sealie Computing", "RET-CUFROM revD", "2/29/08"

The board includes 4x banks worth of full 8KB CHR ram, and 8x 16KB PRG banks.

It is hard-wired for vertical mirroring, and contains 8KB of WRAM mounted in the usual place. There is no battery, but pads are present and suitable for such a purpose if anyone were so inclined. There are no bus conflicts; presumably the other half of the 7420 in the PRG RAM circuit disables the chip's output on writes.

The board contains logic designed for reprogramming from a CopyNES. If EXP0 and R/W go low, /WR reaches the flash ROM. When EXP0 is high, the internal bankswitching register gets accessed.

 Registers:
 ---------------------------
 
 Range,Mask:   $8000-FFFF, $8000
 
   $8000:  [...P PPCC]
     C = CHR RAM bank
     P = PRG ROM bank
 
 PRG Setup:
 ---------------------------
      $8000   $A000   $C000   $E000  
     +-------------------------------+
     |     $8000     |     { -1}     |
     +---------------+---------------+
 
 CHR Setup:
 ---------------------------
       $0000   $1000   
     +-------+-------+
     |     $8000     |
     +-------+-------+

Here's a schematic of the board:

377 O0 --- CRAM A13

377 O1 --- CRAM A14
             ____
A14 ---------\    \
              )    >--- ROM A14
377 O2 ------/____/

             ____
A14 ---------\    \
              )    >--- ROM A15
377 O3 ------/____/

             ____
A14 ---------\    \
              )    >--- ROM A16
377 O4 ------/____/

             ____
EXP0 --------\    \
              )    >--- ROM /WE
R/W ---------/____/

          ,--------------- 377 CLK
          |
          +--------------- ROM /CE
          |   ____
/ROMSEL --+--|    \
             |     )--,
M2 ----------|____/   |
          ,-----------'
          |   ____
          `--|    `-.
             |       \
A14 ---------|        )o-- RAM /CE
             |       /
A13 ---------|____,-'

              ____
EXP0 --------|    `-.
             |       \
+5V ---------|        )o-- 377 /G
             |       /
      ,------|____,-'
      |
      `------------------,
              ____       |
+5V ------+--|    `-.    +-- RAM /OE
          |  |       \   |
          `--|        )o-+-- ROM /OE
             |       /
R/W ------+--|____,-'
          |
          `--------------- RAM /WE