Using with a homebrew 68000 project

Hosted forum for UMDK related questions

Moderators: BigEvilCorporation, prophet36

Post Reply
legacy
Interested
Posts: 13
Joined: Wed Jan 21, 2015 10:46 am

Post by legacy » Sun Feb 08, 2015 12:38 pm

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 ?

User avatar
prophet36
Very interested
Posts: 234
Joined: Sat Dec 13, 2008 6:58 pm
Location: London, UK
Contact:

Post by prophet36 » Sun Feb 08, 2015 1:46 pm

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.
Last edited by prophet36 on Sun Feb 08, 2015 9:29 pm, edited 2 times in total.

legacy
Interested
Posts: 13
Joined: Wed Jan 21, 2015 10:46 am

Post by legacy » Sun Feb 08, 2015 4:33 pm

or two cooperating fpgas

legacy
Interested
Posts: 13
Joined: Wed Jan 21, 2015 10:46 am

Re: Using with a homebrew 68000 project

Post by legacy » Fri Oct 09, 2015 12:30 pm

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

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest