The 3D glasses adapter uses a charge pump triggered by the Z80 Read and Write signals to generate a high voltage to drive the comparator which drives the 3D glasses. Thanks to kamillebidan on SMSPower.org for sharing the schematic.
There are two PCB jumpers found on the Sega Card PCB: M3 & M4. These jumpers control which SMS signal connects to #CRDSEL (pin 3 of the 74HC259).
- M3 shorted connects #CRDSEL to #CE (Pin 13 of Card Slot)
- M4 shorted connects #CRDSEL to #MREQ (Pin 3 of Card Slot)