The AMSSIO interface is a [[RS232]] interface by the dane, [[Martin Zacho]].
As opposed to other serial interfaces the AMSSIO is meant to be installed on top of the [[Z80]] CPU in the CPC. However the circuit can easily be built on a Lochrasterplatine (what's the english word? experimental board?) breadboard and connected to the expansion port as well.
AMSSIO exists in 3 different versions.