Sega Game Gear Cart Pinout
Here's the pinout for the Game Gear cart port. I found it over here.

1+34(V)liquid drive24MREQmemory request
2+5(V)+5(V)25A10/TPR2address
3/WRwrite signal26/RDread signal
4A12address27/EXM 20~7FFFH
5A7/CL1B3address28A15address
6A6/CL1A2address29A11address
7A5/CL1B2address30A9/TPR1address
8A4/CL1A1address31A8/CLIA3address
9A3/CL1B1address32A13address
10A2/DWaddress33A14address
11A1/DO3address34/EXM18000~BFFFH
12A0/DO1address35+5v+5 volts
13D0/DBdata36/M1M1 cycle
14D1/P3data37IORQI/O request
15D2/P2data38/RFSHrefresh
16GND Dground39/RESETReset
17GND Aground40CCLKClock
18GND Dground41GNDGround
19D3/P4data42/GGMS/GG
20D4/P1 data43/TVTV Cart
21D5/CL2data44TVSNDRVR Right Audio
22D6/DO2data45TVSNDLTV Left Audio
23D7/DO4data



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