SpritesMind.Net

what about the cartridge interface ?

i'm thinking about using this UMDK kit to interface my home made 68k board, which has an IDP bus with 32bit data address and space

i do not know the MegaDrive cartridge interface: is it 16 bit data size or 32bit ?

The easiest way to make UMDK work with a homebrew 68000 is to design an alternative bridge-board. Each UMDK card consists of a 4-layer general purpose LX9 FPGA board and a MegaDrive-specific bridge-board. The bridge-board basically just converts the LX9's edge-connector so it's mechanically (i.e connector configuration, mounting holes, etc) and electrically (i.e level-shifters) compatible with the MegaDrive cart slot. An alternative bridge-board can be manufactured cheaply (~$35 for 10x PCBs) and easily soldered at home.

However, the MegaDrive cartridge interface has only 16 data lines and 23 address lines (i.e what you get from a regular 68000 or 68010). Furthermore, the LX9 FPGA board itself has no free I/O pins, and all internal FPGA data paths are only 16 bits wide. Since your homebrew system will not have to deal with the MegaDrive's low-latency DMA cycles, you could alter the memory controller to always do two-word bursts, giving 32 bits. But you'd still need to design or otherwise acquire an FPGA board with sufficient I/Os to externalise that 32-bit data bus. This is doable but the FPGAs having many I/Os tend to be provided in BGA packages, which (although possible to solder at home) are much more difficult to work with.

or two cooperating fpgas

is there someone interested in this project ?
any skilled guy with Or/Eagle/Altium/CAD ?