Master System:Connector Pinouts

AV Out

Note: Connector is the female end at the console. This connector is not present on the NTSC and PAL Master System II.

Pin #	Description
1	Composite Video Out (SMS and Mark III) / Unused (French SMS and French SMS II)
2	Ground
3	Audio Out
4	Green
5	5V
6	Composite Sync
7	Red
8	Blue

Cartridge Port (Mark III and Japanese SMS (MK-2000)

Note: Pins A1 through A22 are towards the back and numbered from left to right. Pins B1 through B22 are towards the front and numbered the same way.

Pin #	Description	Pin #	Description
A1	A0	B1	5V
A2	A1	B2	5V
A3	A2	B3	!CSRAM
A4	A3	B4	!EXM1
A5	A4	B5	!RD
A6	A5	B6	!WR
A7	A6	B7	Unused (Mark III) / !RST (MK-2000)
A8	A7	B8	Unused
A9	A8	B9	Unused (Mark III) / !MREQ (MK-2000)
A10	A9	B10	!MREQ (Mark III) / !CE4 (MK-2000)
A11	A10	B11	CONT
A12	A11	B12	Unused
A13	A12	B13	Unused
A14	A13	B14	Unused
A15	D0	B15	Unused
A16	D1	B16	Unused
A17	D2	B17	Unused
A18	D3	B18	A14
A19	D4	B19	!EXM2
A20	D5	B20	Unused
A21	D6	B21	Ground
A22	D7	B22	Ground

Controller Port

Note: Female is connector at the console. Male is connector at the controller. Diagram pictured is of the connector at the controller end. This pinout is mostly identical to the SG-1000.

Pin #	Description
1	Up
2	Down
3	Left
4	Right
5	Unused
6	Button 1
7	TH/Light Phaser trigger (Master System) / Ground (Mark III, console side only)
8	Ground
9	Button 2

Mark III Expansion Port

This expansion port is only found on the Mark III and is mostly identical to the one in the SG-1000 and SG-1000 II.

Note: Pins are numbered from left to right with the edge of the connector facing forward.

Pin #	Description
1	Ground
2	Ground
3	Ground
4	Ground
5	A2
6	Unused
7	IOREQ
8	CONT
9	Write
10	Read
11	KBSEL
12	D7
13	D6
14	D5
15	D4
16	D3
17	D2
18	D1
19	D0
20	A1
21	A0
22	KILLGA
23	5V
24	5V