Sega Genesis/MegaDrive Expansion Port Pinout

This pinout is took a while to complete. As part of an effort to connect a Teradrive to a SegaCD unit, I had to trace the expansion port. This is it. Some pins are labelled by destination rather than signal, for example 87/315-5364. This means it runs to pin 87 of the IC 315-5364. Also, this refers only to the model 1 Genesis/MegaDrive. There may be minor differences in the model 2, for example the audio in the 2 does not require the patchcord, so I assume there's a small difference there. Some of the pin names may sound a little odd, they're based on corresponding cartridge port pins. The majority of the pins on the expansion port, for example the data and address lines, connect to the same pins on the cartridge port. /C_OE is Cartridge Output Enable, which sounds a little odd on the expansion port, but I'm sure you'll adjust. If you have any additional info on this or the model 2 differences, please email me.

pin Name A01 GND A02 NC A03 /C_OE A04 D00 A05 D01 A06 D02 A07 D03 A08 D04 A09 D05 A10 D06 A11 D07 A12 GND A13 D08 A14 D09 A15 D10 A16 D11 A17 D12 A18 D13 A19 D14 A20 D15 A21 87/315-5364 A22 /LO_MEM A23 91/315-5364 A24 86/315-5364 A25 10/315-5309 A26 +5v A27 NC A28 VCC IN* A29 Audio* A30 GND pin Name B01 GND B02 11/315-5309 B03 A01 B04 A02 B05 A03 B06 A04 B07 A05 B08 A06 B09 A07 B10 A08 B11 A09 B12 GND B13 A10 B14 A11 B15 A12 B16 A13 B17 A14 B18 A15 B19 A16 B20 A17 B21 /LDS B22 /UDSW B23 Cart B21* B24 85/315-5364 B25 10/315-5309 B26 +5v B27 NC B28 VCC IN* B29 Audio* B30 GND * VCC IN - It appears the SGCD is capable of powering the main console through these pins. Power from them is routed directly to the console power switch through a pair of diodes. * Cart B21 - This pin connects to the cartridge slot B21, function unknown. * Audio - This is assumed functional, but is untested.

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