cartridge port info

[DamageX]

I found this page a while back: SEGA Saturn cartridge port pinouts

It seems that some of the signals are still unknown? I unsoldered an ST-Key recently which contained a PAL and a rom. Unsurprisingly the PAL is not readable, but I got a dump of the rom (I think... it didn't want to read correctly as the device which it is labeled as). I'm thinking about getting a 27C1024 to replace it and run my own test code, then I can put a scope on the PAL signals.

Also, there were Saturn schematics on a Japanese site, but I could not determine where the cartridge port lines lead to.

 

[antime]

The scanned service manuals have much more useful pinouts for the cartridge port. We know the names of all the pins, and what they are connected to, but there are a few whose mechanisms are unknown, at least to me. Eg. there's two pins connected to the SMPC. One seems to be an input and the other an output, but these are completely undocumented in the SMPC manual or related headers.

The carts I've seen use PALs and/or GALs for address decoding, and for converting linear addresses to column/row addressing for RAM. You may be able to extract the logic equations from the PAL using Charles MacDonald's tools.

 

[DamageX]

Oh, a service manual... nice. I hadn't seen that.

The ST-Key PAL has A19-A25, D0-D1, and /AWR0 connected to it. I'm guessing it has the capability to remap or disable access to its own ROM. But I don't really need to know this as my goal is just to make my own cart and connect some weird stuff to the Saturn. Like those $5 W5100 boards for Arduino, with ethernet and SD card...

Now that I have the name of every pin, I mostly will just have to check out the timing for some signals.