Oh I definitely would prefer to know why! At work we don't even follow the manufacture's wiring diagrams without first working through it on paper! Though I admit this stuff is a long way away from the programming and wiring I'm used to. Sorry about the accusation, was just trying to get more info than "Its wrong" if your know what I mean... I'm going to sit down with the chip specs at lunch and reread them to hopefully start understanding them better. One I've read through them again would you mind answering some theory questions? Getting away from pin16 to pin## wiring specifics and just talk about how the chip are working.jeffro11 wrote:Not being rude. Just the truth. The best wiring diagram is the one you make yourself. Just go read the datasheets for the decoders, and the eeproms and you'll see that the snesdev diagrams are somewhat wrong (connecting pins that are marked as NC in the datasheets for example). That is seriously the best way to learn. Anyone can copy a diagram and see where to connect things. But wouldn't you rather know WHY your doing it?
I took a quick look at, unless I'm wrong, only half of the '139 is being used. Only the Vcc is being hooked up on pin 16. Its not that the other side is NC, but can be considered NC since it isn't being utilized in this setup! So its taking the trigger from the MAD-1 and the trigger from the mask ROM input to determine which eprom should be
triggered. And they can be stacked, aside from the /CE which needs to be broken out separately to address the eprom, because the other 3 chips will technically be non-existent and only the active chip will output on the bus back to the mask ROM. Is it safe to assume that if the output pins on the eproms are tied together as I have seen that they won't damage the other chips since they aren't active? Still trying to work through the difference between how the MAD-1 operates in HiROM mode and loROM mode...
vlame,
Those are both great resources! I had been using that exact spreadsheet to determine what carts had what specs in common. The mod article is really useful too, from a starting stand point. Unfortunately, it doesn't get into some of the details as to why you are doing what you are doing and as such is limited in usefulness when tackling more complicated setups such as with a line decoder, but a great read nonetheless on what to expect when getting into this kinda hobby! Thanks for digging those up so I can actually bookmark them this time and not loose them in the ton of stuff I was reading.
