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.

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