Master System Cartridge

From HwB

Available at Sega Master System, Master System II and Game Gear (with SMS adapter).

Same pinout also for Master System Expansion port, but upside down.

Korean and Japanese Master System uses different connector.



Front 2           50
      ==============	(at Cartridge)
Back  1           49
Back  39           1
      ==============	(at Console)
Front 50           2
Pin Dir Name Description
1 Arrowr.png +5V Power +5V
2 Arrowr.png /WR Write
3 Arrowr.png /MREQ Memory Request
4 Arrowr.png /RD Read
5 Arrowr.png /EXM1 (/M0-7) Memory 8000-BFFF
6 Arrowr.png A14 Address bit14
7 Arrowr.png A13 Address bit13
8 Arrowr.png A8 Address bit8
9 Arrowr.png A9 Address bit9
10 Arrowr.png A11 Address bit11
11 Arrowr.png /EXM2 (/M8-B) Memory 0000-7FFF
12 Arrowr.png A10 Address bit10
13 Arrowr.png /CE Cartridge Output Enable
14 Arrowlr.png D7 Data bit7
15 Arrowlr.png D6 Data bit6
16 Arrowlr.png D5 Data bit5
17 Arrowlr.png D4 Data bit4
18 Arrowlr.png D3 Data bit3
19 Arrow.png GND Ground
20 Arrow.png GND Ground
21 Arrow.png GND Ground
22 Arrowlr.png D2 Data bit2
23 Arrowlr.png D1 Data bit1
24 Arrowlr.png D0 Data bit0
25 Arrowr.png A0 Address bit0
26 Arrowr.png A1 Address bit1
27 Arrowr.png A2 Address bit2
28 Arrowr.png A3 Address bit3
29 Arrowr.png A4 Address bit4
30 Arrowr.png A5 Address bit5
31 Arrowr.png A6 Address bit6
32 Arrowr.png A7 Address bit7
33 Arrowr.png A12 Address bit12
34 Arrowl.png /CONT A general-purpose input bit that can be read from port $dd bit5
35 Arrowr.png +5V Power +5V
36 Arrowr.png A15 Address bit15
37 Arrowr.png /M1 Indicate machine cycle
38 Arrowr.png /IORQ I/O Request
39 Arrowr.png /RFSH Refresh
40 Arrowr.png /HALT Halt
41 Arrowl.png /WAIT Wait
42  ? Arrowlr.png /INT Interrupt
43 Arrowl.png JyDs (also known as /KILLGA) Dissable joystick registers in IO space
44 Arrowl.png /BUSRQ Bus request
45 Arrowr.png /BUSACK Bus request acknowledge
46 Arrowr.png /RST Reset
47 Arrowr.png CLK Clock
48 Arrowr.png /JREAD Active when access to joystick register region ($c0-$ff) in IO space
49 Arrowr.png /CSRAM (/MC-F) Memory C000-FFFF
50  ? Arrowlr.png /NMI Non Maskable Interrupt

Note: Direction is Console relative Cartridge



  • Japanese and South Korean consoles use 44-pin cartridges, same shape as Mark I and Mark II
  • All other consoles use 50-pin cartridges with a different shape
  • The difference in cartridge style is a form of regional lockout

Cartridges were originally used for game of higher capacity than 256Kb (32KB), smaller ones were stored on cards.

When the Master System II arrived (without a card input), some Card games have been converted to cartridges.

Cartridges bigger than 512Kb (64KB) cannot be used with the 16 address bits and must use FCRs (Frame Control Registers, a bank switching method).

Because cards only have 15 address bits (while cartridges have all the 16 bits) and don't use bank switching, they are limited to 256Kb (32KB), cartridges are used for higher capacities.


  • These are the signal directions you should adhere to, it may be possible to write towards console by using the Bus request mechanism of the Z80. Doing so will let you see only the Internal SRAM, Bios ROM is dissabled normaly via Register. With an I/O Request it may be possible to gain controll over the hardware on the IO Bus, but thats not so simple aswell.
  • If you would like to make something like a ram patcher, better intercept the NMI somehow and do it by software afterwards.