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I am in the process of revamping antime's USB Cart to not be tied to the CS0 line as well as not being tied to any cart in particular. The purpose of this is to allow us to have something more useful than the serial connector.
My current goal for it is to allow us to play Netlink games as well as having access to extended RAM. (I already have Netlink play working with the current USB cart.)
When all is said and done, this mod should be able to be done right on the Saturn's MB, so any cart can be added. This will be especially useful for my SF3 online project as access to the memory card means more saves, and access to 4MB RAM means more online data being stored instead of having to retransfer.
Currently it is planned to work off of the CS2 line using the area that Netlink uses to do its transfers.
Current line of thinking is this:
4 to 16 Demux
A12 must be low.
If A12 is high, then all pins are high, disabling both chips ability to write.
CS2 must be low.
If CS2 is high, then all pins are high, disabling both chips ability to write.
If Write is low, then FT245RL(FIFO) is the only path.
If Read is low and A12 is high, then 74HCT245 (Flags) is the only path
If Read is low and A13 is high, then FT245RL (FIFO) is the only path.
Else both chips ability to read are disabled.
0x25802XXX is used for Flags
0x25803XXX is invalid.
0x25804XXX is used for FIFO
There is mirroring as only A13 and A14 are checked, so as long as one of those is high, you will get results.
Should be safe with Netlink as pin 12 is required to be high.
Should be safe from CS2 as it falls within the allowed range like Netlink does
Now I am not a hardware guy, so I am sure there may be things I am overlooking.
Added a new pic mapping the 4MB cart pins since I am going to use this for now.
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