Connectors

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Notes

  • Input mean from device (cart or megacd for example) to Megadrive.
  • Output mean from MegaDrive to device

Cartridge Connector

MegaDrive Mode

Front Side Back Side
Pin Number Name I/O Description Pin Number Name I/O Description
B01 SL1 Input Left audio from cart A01 GND Ground
B02 /MRES Unknow Active low

hard (bootup) reset

A02 Vcc1 Output Positive supply voltage (+5V)
B03 SR1 Input Right audio from cart A03 VA8 Output
B04 VA09 Output A04 VA11 Output
B05 VA10 Output A05 VA7 Output
B06 VA18 Output A06 VA12 Output
B07 VA19 Output A07 VA6 Output
B08 VA20 Output A08 VA13 Output
B09 VA21 Output A09 VA5 Output
B10 VA22 Output A10 VA14 Output
B11 VA23 Output A11 VA4 Output
B12 /YS Output Active low

Mean that VDP is currently drawing the backdrop color

A12 VA15 Output
B13 /VSYNC Output Active low

Vertical Sync

A13 VA03 Output
B14 /HSYNC Output Active low

Horizontal Sync

A14 VA16 Output
B15 EDCLK Output VDP related clock, variable, changes between Mclk/5 ~ Mclk/4 A15 VA2 Output
B16 /CAS0 Output Active low

set for reads on $000000-$DFFFFF acts as /OE signal

A16 VA17 Output
B17 /CEO Output Active low

Chip Enable set for r/w at/to $000000-$3FFFFF when cart is inserted or at/to $400000-$7FFFFF when not

A17 VA01 Output
B18 /AS Output Active low

Address Strobe - addr bus valid

A18 GND Ground
B19 VCLK Output 68k clock A19 VD7 Input/Output
B20 /DTAK Input Data Transfer acKnowledge for 68k A20 VD0 Input/Output
B21 /CAS2 Unknown Unknown A21 VD8 Input/Output
B22 VD15 Input/Output A22 VD6 Input/Output
B23 VD14 Input/Output A23 VD01 Input/Output
B24 VD13 Input/Output A24 VD09 Input/Output
B25 VD12 Input/Output A25 VD05 Input/Output
B26 /ASEL Output Active low

set for r/w at/to $000000-$7FFFFF

A26 VD02 Input/Output
B27 /VRES Output Reset from switch A27 VD10 Input/Output
B28 /LWR Output Active low

Lower byte WRite

A28 VD04 Input/Output
B29 /UWR Output Active low

Upper byte WRite

A29 VD03 Input/Output
B30 /M3 Input Active low

Force Mark 3 (Master System) mode

A30 VD11 Input/Output
B31 /TIME Output set for r/w at/to $A13000-$A130FF A31 Vcc1 Output Positive supply voltage (+5V)
B32 /CART Input Active low

set when cart is inserted

A32 GND Ground

SMS Mode

Front Side Back Side
Pin Number Name I/O Description Pin Number Name I/O Description
B01 SL1 Input Left audio from cart A01 GND Ground
B02 /MRES Unknow Active low

hard (bootup) reset

A02 Vcc1 Output Positive supply voltage (+5V)
B03 SR1 Input Right audio from cart A03 VA07 Output
B04 VA08 Output A04 VA10 Output
B05 VA09 Output A05 VA06 Output
B06 /CE Output A06 VA11 Output
B07 ? ? A07 VA05 Output
B08 ? ? A08 VA12 Output
B09 plup Output A09 VA04 Output
B10 pldn Output A10 VA13 Output
B11 /NMI Output A11 VA03 Output
B12 ? ? A12 VA14 Output
B13 ? ? A13 VA02 Output
B14 ? ? A14 ? ?
B15 ? ? A15 VA01 Output
B16 /RD Output A16 ? ?
B17 /M0-7 Output A17 VA00 Output
B18 ? ? A18 GND Ground
B19 ? ? A19 VD07 Input/Output
B20 ? ? A20 VD00 Input/Output
B21 ? ? A21 ? ?
B22 ? ? A22 VD06 Input/Output
B23 ? ? A23 VD01 Input/Output
B24 ? ? A24 ? ?
B25 ? ? A25 VD05 Input/Output
B26 ? ? ? A26 VD02 Input/Output
B27 ? ? A27 ? ?
B28 /Wr Output A28 VD04 Input/Output
B29 ? ? A29 VD03 Input/Output
B30 /M3 Input Active low

Force Mark 3 (Master System) mode

A30 ? ?
B31 ? ? A31 Vcc1 Output Positive supply voltage (+5V)
B32 /CART Input Active low

set when cart is inserted

A32 GND Ground

Expansion connector

Front Side Back Side
Pin Number Name I/O Description Pin Number Name I/O Description
B01 GND A01 GND
B02 VA19 Only on MegaDrive 2 boards A02 /DISK
B03 /CAS0 A03 VA01
B04 VD00 A04 VA02
B05 VD01 A05 VA03
B06 VD02 A06 VA04
B07 VD03 A07 VA05
B08 VD04 A08 VA06
B09 VD05 A09 VA07
B10 VD06 A10 VA08
B11 VD07 A11 VA09
B12 GND A12 GND
B13 VD08 A13 VA10
B14 VD09 A14 VA11
B15 VD10 A15 VA12
B16 VD11 A16 VA13
B17 VD12 A17 VA14
B18 VD13 A18 VA15
B19 VD14 A19 VA16
B20 VD15 A20 VA17
B21 /ROM A21 /LWR
B22 /ASEL A22 /UWR
B23 /RAS2 A23 /CAS2
B24 /FDC A24 /FDWR
B25 FRES A25 VA18 Only on MegaDrive 2 boards
B26 Vcc1 A26 Vcc1
B27 SR3 Only on MegaDrive 2 boards A27 SL3 Only on MegaDrive 2 boards
B28 9V A28 9V
B29 SR2 A29 SL2
B30 GND A30 GND