Schematic

This is the simplest version of the Supercart. It supports up to 8, 16K banks of ROM.. The banks are mapped into an address range from $8000-$BFFF. To change banks the bank number is written to any address from $8000-$BFFF. The ROM chip (U1) is enabled by the logic circuit composed of U4C and U3D. The logic circuit composed of U3A, U4A, and U4B latches the bank number into U2 on a write. When the address range $C000-$FFFF is read, U2 is disabled and the resistors R2,R3, and R4 set the bank number to 7, so that bank 7 always appears in that address range. When address range $4000-$7FFF is read U4D sets bit 0 of the bank number low, selecting bank 6 into this address range.