I am trying to implement an SCC mapper so that I don't need to use real SCC chips for the SD interface from sharksym. This will save some roms in the future 
The basis for this mapper is Jipes schematic posted at HansO site
It works fine for some roms but not for all. I can get Space Manbow to work but not Metal Gear 2 or even worse the MMC bios rom does not work either.
As an SCC mapper looks at address 5000, 7000, 9000 and b000
A15 and A13 are used to select register address in the ls670 and A11 and /A12 are used to enable the write to the ls670. D0-D5 are used for bank selecting. In theory it looks right but my msx thinks otherwise. Am I missing something?
I have a more thorough design now ready to test tonight to see if that works better.
It only enables the write to the ls670 when data is written to addresses:
5000 - 57ff, 7000 - 77ff, 9000 - 97ff and b000 - b7ff
Can someone help me in implementing a full working SCC mapper so I can make cheap SD interfaces for everyone interested in this device?
