Cartridge Pinout

This table is originally from David Tucker, and I've just added the recently found pins.

*Notes:

Pins 55-58 are analog sound pins that the VB goes through between the sound source and the speakers. My guess it that they would have been used in the future for an audio enhancement chip, much like the Super Nintendo used.

Pins 10,12,14 are the last 3 addresses that were never used on the VB, but that means that the VB supports up to a 128 mbit chip! That would be a nice multicart! ;-)

Pin 4 is /ES which is the expansion area select, which was to be used in the future for addon chips, similar to the SuperFX and other chips used on the SNES.

Pin 9 is /INTCRO, which is the interrupt for the expansion area.

Pin 5 is /WE. When writing to a memory location, this pin is pulled low (perfect for writing flash in-system)

Pin 7 is connected to CS2 (active high chip select) on the cart SRAM, but watching the pin on the oscilloscope, it doesn't appear to change during SRAM access.  It isn't physically connected directly to +5V, so don't use it for power, and it shouldn't be connected to the +5V bus, but I'd recommend not designing anything to use that pin without first verifying that it works the way you expect.

Edge 
Con        ROM         RAM
---        ---         ---
 1 (gnd)
 3                     27 (/WE)
 5 /WE
 7                     26 (CS2)
 9 /INTCRO
11         2 (A18)
13         3 (A17)
15         4 (A7)       3 (A7)
17         5 (A6)       4 (A6)
19         6 (A5)       5 (A5)
21         7 (A4)       6 (A4)
23         8 (A3)       7 (A3)
25         9 (A2)       8 (A2)
27        10 (A1)       9 (A1)
29        11 (A0)      10 (A0)
31        12 (/CE)
33 (gnd)  13 (GND)
35        14 (/OE)     22 (/OE)
37        15 (D0)      11 (D0)
39        16 (D8)
41        17 (D1)      12 (D1)
43        18 (D9)
45        19 (D2)      13 (D2)
47        20 (D10)
49        21 (D3)      15 (D3)
51        22 (D11)
53 (+5v)
55 (Right Analog Audio Source)
57 (Right Analog Audio Output)
59 (gnd)
----------------------------
 2 (gnd)
 4 /ES (Expansion Select)
 6                     20 (/CS1)
 8 (+5v)
10           (A22)
12           (A21)
14        44 (A20)
16        43 (A19)
18        42 (A8)      25 (A8)
20        41 (A9)      24 (A9)
22        40 (A10)     21 (A10)
24        39 (A11)     23 (A11)
26        38 (A12)     2  (A12)
28        37 (A13) 
30        36 (A14)
32        35 (A15)
34        34 (A16)
36 (+5v)  33 (/BYTE)
38        31 (D15)
40        30 (D7)      19 (D7)
42        29 (D14)
44        28 (D6)      18 (D6)
46        27 (D13)
48        26 (D5)      17 (D5)
50        25 (D12)    
52        24 (D4)      16 (D4)
54 (+5v)  23 (Vdd)
56 (Left Analog Audio Source)
58 (Left Analog Audio Output)
60 (gnd)