This is a simple ROM card for the Apple IIGS that contains an 8KB D-Net ROM and 8KB of SRAM. This is similar to the Digicard D-Net card for Apple II computers except that this card contains no serial ports in favor of using the Apple IIGS’ built-in serial ports.

Every D-Net card has a unique identifier, printed on the ROM, which is stored in the ROM as 4 bytes in little endian byte order at offsets 0xfb4 and 0x1fb4.

An additional pin header TP on the card is typically connected to pin 1 (the /IOSEL signal) in slot 1 using a dummy expansion card. This lets the card provide two different boot ROMs - one for the slot that the network card is installed in to provide a network booting feature, and one for slot 1 to provide a network printing feature.

Schematic

KiCad Project & all artifacts

Front Image

Back Image

Slot 1 Dummy Card