Need info on how to SMS compatiblity on SMD/SG

[zxcvbnm]

Does anyone know which pins in the megadrive cartridge slot activate compatipablity for master system games and what state they must be in?

I know it doesn't need any extra electrical components to activate because I have an adapter that only changes the pinout.

Please include the physical location of the pins so there is no confusion.

Any help will be much appreciated.  

[viletim!]

I have this info written down on a bit of paper somewhere...I'll have a look for it tonight.

[viletim!]

When I last looked at this I was trying to work out what would be needed to connect a rom to the cart port and have the mega drive read from it in normal mega-drive mode and in master system mode by just flicking a switch. My notes are messy but here's what I can tell you....

Refer to the gamesx megadrive pinout.
Pull B30 low to put the console into master system mode (Soft reset is a misnomer). This line is normaly held high by a pull up resistor. When in master system mode some of the cart pins change function....i'll make a table.

Code Select Expand

PIN|   NORMAL|   MS-MODE|
xx      A1-15      A0-14 (no change, just different names)
B06       A18        !CE
B17       !CE        A15
B11       A23      PAUSE (input! low = paused)
B09       A21        ??? (pull high, dunno why)

Everything else should be as you'd expect. I have not investigated the other unused address pins.

[zxcvbnm]

Thanks a lot for the info it has been very helpful.