Asynchronous Disconnect Mode (ADM) is an auxiliary operating mode of the HDLC protocol. In this operating mode, which applies to slave stations and hybrid stations, the station may neither send nor receive data
or control blocks.ADM operation represents a ready state for the link layer. This state can be left or entered at any time by either of the two corresponding communication partners. The task of ABM operation is to initialize the data connection between two corresponding systems at the right moment and to switch to Asynchronous Balanced Mode (ABM).