Two or more active expanders can be cascaded.

The master module feeds data to the module to the MOSI in pin.

When chaining or cascading modules you need to connect the MOSI cascade out to the MOSI in on the next Digital8 Expander down the chain.

All the other signals, GND, +5V, SS and SCK should be connected in parallell for all the expanders. Only the MOSI in and MOSI cascade out are connected in serial chain.

Read the manual for the master module to see how many Digital8 Expanders it can support. Normally only one.