Disclosed are a system, method and device for negotiating a data transmission mode over an attachment unit interface (DDI). A data transceiver circuit may be coupled to one or more data lanes of the DDI. A negotiation section may receive a link pulse signal on at least one data lane in the DDI during a negotiation period and selectively configure the data transceiver to transmit and receive data on one or more data lanes according to a data transmission mode based upon the received link pulse signal.