Cartridge Pinout (Sega Mega-Tech)

the sega mega tech cartridges have a different pinout than the mega drive the a side is identical, but the b side is different you cannot just directly re wire a mega drive game to the different pins, you will also require a rom chip loaded with some header information too that presents the game title and descriptions to the mega tech sms menu system both header and game roms have their !e pin (chip enable when low) wired to !ce0 the header rom is typically a m27c256, with its !g pin (output enable when low) wired to the header !oe pin the game rom has its !g pin (output enable when low) wired to !cas0 that means when the system wants to read from the cartridge at all it first sets ce0 to low when it wants to read header information it sets the !header oe to low, and !cas0 to high when it wants to read the game rom it sets the !header oe to high and !cas0 to low below are the pinouts of the mega tech cartridge note directions relate to the mega tech side so, an audio as input means the cartridge pin is an output to the mega tech an address pin as output means the mega tech is outputting an address to the cartridge pin direction designation description a1 output gnd a2 output +5v a3 output address bit 8 a4 output address bit 11 a5 output address bit 7 a6 output address bit 12 a7 output address bit 6 a8 output address bit 13 a9 output address bit 5 a10 output address bit 14 a11 output address bit 4 a12 output address bit 15 a13 output address bit 3 a14 output address bit 16 a15 output address bit 2 a16 output address bit 17 a17 output address bit 1 this is the first address bit, bit 0 is hardwired to low a18 output gnd a19 output / input data bit 7 a20 output / input data bit 0 a21 output / input data bit 8 a22 output / input data bit 6 a23 output / input data bit 1 a24 output / input data bit 9 a25 output / input data bit 5 a26 output / input data bit 2 a27 output / input data bit 10 a28 output / input data bit 4 a29 output / input data bit 3 a30 output / input data bit 11 a31 output +5v a32 output gnd pin direction designation description b1 output /vres system reset, from front panel switch b2 output /mres master reset, from system start up b3 b4 output address bit 9 b5 output address bit 10 b6 output address bit 18 b7 output address bit 19 b8 output address bit 20 b9 output address bit 21 b10 output address bit 22 b11 output address bit 23 b12 b13 b14 output header !oe read from header rom the !oe pin going to the header rom b15 b16 b17 b18 output /as address strobe, address on bus is currently valid and not changing b19 b20 input /dtack data acknowledge to 68k b21 b22 output / input data bit 15 b23 output / input data bit 14 b24 output / input data bit 13 b25 output / input data bit 12 b26 output /cart pulled high in console, cartridge shorts to ground to indicate presence b27 output /ceo chip enable for the cartridge normally low when accessing $000000 $3fffff region when expension unit is present then low when accessing $400000 $7fffff b28 output /lwr lower byte write, the lower byte on the data lines should be written to the location in the address lines b29 output /uwr upper byte write, the upper byte on the data lines should be written to the location in the address lines b30 input /m3 pulled high in console, cartridge shorts to ground to indicate console should run in mark 3 (master system) mode b31 output /time set for r/w at/to $a13000 $a130ff, given the name suggests it might be for a real time clock in the cartridge this would enable usage as a chip enable on a rtc, using fewer address lines or logic to that rtc used in sonic 3 for sram b32 output /cas0 read from game rom read or write on $000000 $dfffff region cartridge examples the mega tech can read both the header info or game info most games use a single game rom and a header rom and some games like after burner also have an additional paging chip uses as a memory chip and sometimes game save