Quoted from DumbAss:Last night I spent a little bit of time looking at the Data East CPU board schematic to build a plan for the board. It's obviously 90%+ identical to the Williams System 11 CPU board but there are differences. I have ideas for an approach but want to solicit opinion because I can try to think of reasons one way or the other but the truth is that the more people who have thoughts and inputs the better the solution will be. I don't believe in "I alone can build it" but I do believe in "I alone will build it and be responsible for it".
I intend to use the System 11 schematic capture that I have due to the identical 90%+ electrical connections. There are few things that fall out from this.
1) Do I somehow try to make a "new" universal board that supports both Williams and Data East circuitry in a single board? This is the Rottendog approach for MPU004. It has pros and cons. One pro is a single board to support everything so no need to maintain separate board inventory or potentially component inventory. One con is that the EPROM size jumpers and address line connections are different between the Data East schematic and the Williams schematic. Another con is it will require configuration settings meaning that the user may be required to change settings and any time a user is involved there is potential for error. I know that MPU004 has DIP settings for the switch solenoids and this is obviously a problem because it's documented on the PinWiki page (https://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Special_solenoid_problems_with_RottenDog_MPU_board).
2) Do I make a separate Data East only board that supports the Data East jumpers (J1-J7) and the Data East special solenoid configuration? This minimizes confusion to the end user but means I have a dedicated board with separate inventory.
3) As a follow on from the differences in the special solenoid configuration it might be possible to make a "bridge board" that bridges the Williams configuration to the Data East configuration and sits between the playfield connector and the board header (much like the special solenoid fuse board). This is a simple end user solution but the end user still needs to remember to install the board (just like the end user would need to set the DIP switches). Human input involvement = potential for error. Nonetheless ... is this a good compromise?
4) If I do go down a complete separate board for Data East do I keep the Williams physical layout that I already have and make modifications to the physical layout to support the schematic changes? Or do I scrap the Williams physical layout and reproduce the Data East physical layout? Keeping the Williams layout will make time to market MUCH faster because I don't have to re-layout 90%+ of the components and traces. Reproducing the Data East layout will make working on the board easier for those who only have experience with the original Data East layout rather than having to get familiar with the Williams layout and potentially translate between the two different layouts.
Hmmm. That's a lot for the reader to contemplate. First world problems. <sigh>.
Any input, feedback or comments are welcome. In the meantime I still need to work through the Data East schematic to identify and collate the differences between it and the Williams schematic to make sure I have a solid foundation to build on.
I don't know if this helps or not, but the only thing different between a DE -3 MPU and an 11C is the pinouts for the special solenoids. I have been running a DE MPU in my Rollergames for years now. For your design, if you use a reset generator, there is no need for +12v on the board at all. However, if you want this board to be compatible with 11/11A/11B also, then you will have to put some thought into the sound section and keep the +12v.
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