the first pin is a CONFIG_IN# signal that comes on pin 12. if it is ground, then the card decodes the address space at E8xxxx -- the Amiga autoconfig space. this pin is always grounded on the A1000. once the card completes its config, it remaps that space to somewhere else in memory, and then pulls the CONFIG_DONE# line low, signaling the next sidecar expansion to do its autoconfig.
this is very similar to how autoconfig is done on the later Amigas, which uses pin 12 and pin 11 to create a "daisy chain" config mechanism.