Expansion Connector Pinout [made by Kevin Horton (khorton@iquest.net)]
--------------------------
+-------\
+5V |01 48| +5V
GND |02 47| GND
Audio In |03 46| NC
R/W |04 45| Out2 (from CPU)
A15 |05 44| Out1 (from CPU)
cart con. pin #51 |06 43| Out0 (from CPU- strobe on sticks)
Cart con. pin #52 |07 42| Cart con. pin #16
Cart con. pin #53 |08 41| Cart con. pin #17
Cart con. pin #54 |09 40| Cart con. pin #18
Cart con. pin #55 |10 39| Cart con. pin #19
/OE for stick 2 |11 38| Cart con. pin #20
Player #1 D1 |12 37| /OE for stick 1
Player #1 D3 |13 36| Player #1 D4
/IRQ |14 35| Player #1 D0
Player #2 D2 |15 34| /OE for stick 1
Player #2 D3 |16 33| Player #1 D2
/OE for stick 2 |17 32| D0
Player #2,D4 |18 31| D1
Player #2,D0 |19 30| D2
Player #2,D1 |20 29| D3
Audio out |21 28| D4
Video out |22 27| D5
+9V |23 26| D6
4.00MHz CLK |24 25| D7
+-------/
Expansion Connector
NOTES: Pins 06-10 and 38-42 Come directly from the cartridge connector. With
those pins, you can pass 10 bits of whatever you like to/from the
expansion port to/from a cartridge board.