Sunsoft 4 pinout

Sunsoft 4: 40-pin 0.6" PDIP

              .---\/---.
        M2 -> | 01  40 | -- +5V
   /ROMSEL -> | 02  39 | <- R/W
   CPU A14 -> | 03  38 | <- CPU D6
   CPU A13 -> | 04  37 | <- CPU D5
   CPU A12 -> | 05  36 | <- CPU D4
  PPU /A13 -> | 06  35 | <- CPU D3
   PPU A12 -> | 07  34 | <- CPU D2
   PPU A11 -> | 08  33 | <- CPU D1
   PPU A10 -> | 09  32 | <- CPU D0
      ?GND -> | 10  31 | <- OR A (PPU /RD)
   PRG /CE <- | 11  30 | <- OR B (SS4 /CHRSEL)
   CHR A17 <- | 12  29 | -> OR Y (CHR /CS)
   CHR A16 <- | 13  28 | -> CIRAM /CS
   CHR A15 <- | 14  27 | -> SS4 /CHRSEL
   CHR A14 <- | 15  26 | -> WRAM /CE
   CHR A13 <- | 16  25 | -> PRG A14
   CHR A12 <- | 17  24 | -> PRG A15
   CHR A11 <- | 18  23 | -> PRG A16
   CHR A10 <- | 19  22 | -> PRG A17
       GND -- | 20  21 | -> WRAM +CE
              `--------'
 
 10 probably actually some control, not a supply pin
 19 also connects to CIRAM A10
 29,30,31 actually just an OR gate; for use with a 28-pin 128KB CHR-ROM

Reference: Naruko's notes