MMC5 pinout

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     80    51
     |     |
     .------.
  81-|      |-50
     | MMC5 |
 100-|      |-31
     \------'
      |    |
      01   30
Pin Function Pin Function Pin Function Pin Function
1 Amplifier Input 51 CPU A6
2 DAC? 52 CPU A7
3 Pulse Waves 53 CPU A8
4 VCC 54 CPU A9
5 PPU A0 55 CPU A10
6 PPU A1 31 CIRAM /CE 56 PRG RAM VCC 81 (unk. output)
7 PPU A2 32 CIRAM A10 57 +batt 82 (unk. output)
8 PPU A3 33 PPU /WR 58 CPU A11 83 PRG RAM +CE
9 PPU A4 34 PPU /RD 59 CPU A12 84 PPU D0
10 PPU A5 35 /IRQ 60 PRG A13 85 PPU D1
11 PPU A6 36 CPU D0 61 PRG A14 86 PPU D2
12 PPU A7 37 CPU D1 62 PRG A15 87 PPU D3
13 PPU A8 38 CPU D2 63 PRG A16 88 PPU D4
14 PPU A9 39 CPU D3 64 PRG A17 89 PPU D5
15 CHR A10 40 CPU D4 65 PRG A18 90 PPU D6
16 CHR A11 41 CPU D5 66 PRG A19 91 PPU D7
17 CHR A12 42 CPU D6 67 CPU A13 92 (unk. output)
18 CHR A13 43 CPU D7 68 CPU A14 93 (unk. output)
19 CHR A14 44 VCC 69 PRG RAM A13 94 CHR A0 †
20 CHR A15 45 CPU A0 70 PRG RAM A14 95 CHR A1 †
21 CHR A16 46 CPU A1 71 PRG RAM 0 /CE 96 CHR A2 †
22 CHR A17 47 CPU A2 72 PRG RAM 1 /CE 97 CL3 †
23 CHR A18 48 CPU A3 73 (unk. output) 98 SL3 †
24 CHR A19 49 CPU A4 74 PRG /CE 99 GND
25 PPU A10 50 CPU A5 75 (unk. output) 100 Amplifier output
26 PPU A11 76 PRG RAM /WE
27 PPU A12 77 CPU R/W
28 PPU A13 78 /ROMSEL
29 (unk. output) 79 M2
30 (unk. output) 80 GND

†PINS 94 thru 98: These set the cart to either CL or SL mode.

To set to CL mode:

  • Connect PPU A0 from the NES to A0 on the CHR ROM.
  • Connect PPU A1 from the NES to A1 on the CHR ROM.
  • Connect PPU A2 from the NES to A2 on the CHR ROM.
  • Connect pins 97 and 98 together.
  • Leave pins 94,95 & 96 floating on the MMC5

To set to SL mode:

  • Connect pin 94 of the MMC5 to A0 of the CHR ROM.
  • Connect pin 95 of the MMC5 to A1 of the CHR ROM.
  • Connect pin 96 of the MMC5 to A2 of the CHR ROM.
  • Connect pin 98 to ground.
  • Leave pin 97 floating.

In other words, CL mode passes the lowest PPU address bits straight to CHR ROM, while SL mode runs them through MMC5. SL mode allows the MMC5 to perform smooth vertical scrolling in split mode, while CL mode does not. Nearly all MMC5 cartridges use CL mode - it is not known why SL mode was not used instead: possibly ROM speed issues.

Audio circuit topology for HVC-ExROM boards:

MMC5 audio.png