You can also connect proper NE2000 compatible Realtek 8019 ISA network card to Atari ST cartridge port using nothing more than a single 74LS245 chip (1). Especially impressive once you investigate cartridge port and learn its READ only :-), no write strobe available. The hack involves treating one of two Rom Chip Select signals as free Address Decoder and actual Address Bus as data bus. (2) There are two Rom Chip Select signals responsible for 0xFA0000 and 0xFB0000 addresses. In order to wrangle a WRITE out of read only port we translate it into reading from 0xFAxxxx where xxxx is our output value. This is also how a Covox like 12bit sound cartridge bundled with a game B.A.T. worked (game used it for digital audio and copy protection).

1/ https://sites.google.com/site/probehouse/networking-the-atar...

2/ https://www.atarimagazines.com/startv1n3/CartridgeSlot.html

3/ https://www.atari-forum.com/viewtopic.php?f=4&t=30389&start=...