This iniLabs page[1] has a description, it's pretty low-level stuff: The AER protocol is a simple protocol using a variable number of lines (bus) to transmit d

This iniLabs page[1] has a description, it's pretty low-level stuff: The AER protocol is a simple protocol using a variable number of lines (bus) to transmit data, and two lines (REQ and ACK) to synchronize the data between the sender and the receiver asynchronously using a four-phase handshake. (This is also called a bundled asynchronous protocol). The ACK and REQ lines are active-low. From the last sentence, it's clear that "line" refers to a hardware signal. It's a chip-to-chip bus protocol, from what I understand. [1] http://inilabs.com/support/hardware/aer/ http://inilabs.com/support/hardware/aer/