Asynchronous Balanced Mode

Asynchronous Balanced Mode (ABM) is a communication mode of HDLC and derivative protocols, supporting peer-oriented point-to-point communications between two nodes, where either node can initiate transmission.

For systems that work in the ABM (Asynchronous Balanced Mode), there is no master/slave relationship. Each station may initialize, supervise, recover from errors, and send frames at any time. The DTE (Data Terminal Equipment) and DCE (Data circuit-terminating equipment) are treated as equals. The initiator for Asynchronous Balanced Mode sends an SABM.